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0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/23.optionals-orelse-unreachable.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "orelse unreachable" {
const a: ?f32 = 5;
const b = a orelse unreachable;
const c = a.?;
try expect(b == c);
try expect(@TypeOf(c) == f32);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/18.integer-casting.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "@intCast" {
const x: u64 = 200;
const y = @as(u8, @intCast(x));
try expect(@TypeOf(y) == u8);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/25.payload-captures-optional-if.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "optional-if" {
const maybe_num: ?usize = 10;
if (maybe_num) |n| {
try expect(@TypeOf(n) == usize);
try expect(n == 10);
} else {
unreachable;
}
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/08.error-set.zig | const FileOpenError = error{
AccessDenied,
OutOfMemory,
FileNotFound,
};
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/30.vectors-looping.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "vector looping" {
const x = @Vector(4, u8){ 255, 0, 255, 0 };
const sum = blk: {
var tmp: u10 = 0;
var i: u8 = 0;
while (i < 4) : (i += 1) tmp += x[i];
break :blk tmp;
};
try expect(sum == 510);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/24.comptime-ints.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "comptime_int" {
const a = 12;
const b = a + 10;
const c: u4 = a;
const d: f32 = b;
try expect(c == 12);
try expect(d == 22);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/18-integer-rules.mdx | import CodeBlock from "@theme/CodeBlock";
import IntegerWidening from "!!raw-loader!./18.integer-widening.zig";
import IntegerCasting from "!!raw-loader!./18.integer-casting.zig";
import IntegerSafeOverflow from "!!raw-loader!./18.integer-safe-overflow.zig";
# Integer Rules
Zig supports hex, octal and binary integer literals.
```zig
const decimal_int: i32 = 98222;
const hex_int: u8 = 0xff;
const another_hex_int: u8 = 0xFF;
const octal_int: u16 = 0o755;
const binary_int: u8 = 0b11110000;
```
Underscores may also be placed between digits as a visual separator.
```zig
const one_billion: u64 = 1_000_000_000;
const binary_mask: u64 = 0b1_1111_1111;
const permissions: u64 = 0o7_5_5;
const big_address: u64 = 0xFF80_0000_0000_0000;
```
"Integer Widening" is allowed, which means that integers of a type may coerce to
an integer of another type, providing that the new type can fit all of the
values that the old type can.
<CodeBlock language="zig">{IntegerWidening}</CodeBlock>
If you have a value stored in an integer that cannot coerce to the type that you
want, [`@intCast`](https://ziglang.org/documentation/master/#intCast) may be
used to explicitly convert from one type to the other. If the value given is out
of the range of the destination type, this is detectable illegal behaviour.
<CodeBlock language="zig">{IntegerCasting}</CodeBlock>
Integers, by default, are not allowed to overflow. Overflows are detectable
illegal behaviour. Sometimes, being able to overflow integers in a well-defined
manner is a wanted behaviour. For this use case, Zig provides overflow
operators.
| Normal Operator | Wrapping Operator |
| --------------- | ----------------- |
| + | +% |
| - | -% |
| \* | \*% |
| += | +%= |
| -= | -%= |
| \*= | \*%= |
<CodeBlock language="zig">{IntegerSafeOverflow}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/25.payload-captures-error-union-if.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "error union if" {
const ent_num: error{UnknownEntity}!u32 = 5;
if (ent_num) |entity| {
try expect(@TypeOf(entity) == u32);
try expect(entity == 5);
} else |err| {
_ = err catch {};
unreachable;
}
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/07.defer.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "defer" {
var x: i16 = 5;
{
defer x += 2;
try expect(x == 5);
}
try expect(x == 7);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/27-opaque.md | # Opaque
[`opaque`](https://ziglang.org/documentation/master/#opaque) types in Zig have
an unknown (albeit non-zero) size and alignment. Because of this these data
types cannot be stored directly. These are used to maintain type safety with
pointers to types that we don't have information about.
<!--fail_test-->
```zig
const Window = opaque {};
const Button = opaque {};
extern fn show_window(*Window) callconv(.C) void;
test "opaque" {
var main_window: *Window = undefined;
show_window(main_window);
var ok_button: *Button = undefined;
show_window(ok_button);
}
```
```
./test-c1.zig:653:17: error: expected type '*Window', found '*Button'
show_window(ok_button);
^
./test-c1.zig:653:17: note: pointer type child 'Button' cannot cast into pointer type child 'Window'
show_window(ok_button);
^
```
Opaque types may have declarations in their definitions (the same as structs,
enums and unions).
<!--no_test-->
```zig
const Window = opaque {
fn show(self: *Window) void {
show_window(self);
}
};
extern fn show_window(*Window) callconv(.C) void;
test "opaque with declarations" {
var main_window: *Window = undefined;
main_window.show();
}
```
The typical usecase of opaque is to maintain type safety when interoperating
with C code that does not expose complete type information.
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/29.sentinel-termination-string-literal.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "string literal" {
try expect(@TypeOf("hello") == *const [5:0]u8);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/_category_.json | {
"label": "Language",
"link": {
"description": "Getting started with the Zig programming language."
}
} |
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/21-labelled-loops.md | # Labelled Loops
Loops can be given labels, allowing you to `break` and `continue` to outer
loops.
```zig
test "nested continue" {
var count: usize = 0;
outer: for ([_]i32{ 1, 2, 3, 4, 5, 6, 7, 8 }) |_| {
for ([_]i32{ 1, 2, 3, 4, 5 }) |_| {
count += 1;
continue :outer;
}
}
try expect(count == 8);
}
```
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/08.error-set-inferred.zig | fn createFile() !void {
return error.AccessDenied;
}
test "inferred error set" {
//type coercion successfully takes place
const x: error{AccessDenied}!void = createFile();
//Zig does not let us ignore error unions via _ = x;
//we must unwrap it with "try", "catch", or "if" by any means
_ = x catch {};
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/14-slices.mdx | import CodeBlock from "@theme/CodeBlock";
import Slices from "!!raw-loader!./14.slices.zig";
import Slices2 from "!!raw-loader!./14.slices-2.zig";
# Slices
Slices can be thought of as a pair of `[*]T` (the pointer to the data) and a
`usize` (the element count). Their syntax is `[]T`, with `T` being the child
type. Slices are used heavily throughout Zig for when you need to operate on
arbitrary amounts of data. Slices have the same attributes as pointers, meaning
that there also exists const slices. For loops also operate over slices. String
literals in Zig coerce to `[]const u8`.
Here, the syntax `x[n..m]` is used to create a slice from an array. This is
called **slicing**, and creates a slice of the elements starting at `x[n]` and
ending at `x[m - 1]`. This example uses a const slice, as the values to which
the slice points need not be modified.
<CodeBlock language="zig">{Slices}</CodeBlock>
When these `n` and `m` values are both known at compile time, slicing will
actually produce a pointer to an array. This is not an issue as a pointer to an
array i.e. `*[N]T` will coerce to a `[]T`.
<CodeBlock language="zig">{Slices2}</CodeBlock>
The syntax `x[n..]` can also be used when you want to slice to the end.
```zig
test "slices 3" {
var array = [_]u8{ 1, 2, 3, 4, 5 };
var slice = array[0..];
_ = slice;
}
```
Types that may be sliced are arrays, many pointers and slices.
:::info
We can now apply our knowledge and [make another program together](/posts/fahrenheit-to-celsius).
:::
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/24-comptime.mdx | import CodeBlock from "@theme/CodeBlock";
import ComptimeBlocks from "!!raw-loader!./24.comptime-blocks.zig";
import ComptimeInts from "!!raw-loader!./24.comptime-ints.zig";
import ComptimeTypeBranching from "!!raw-loader!./24.comptime-type-branching.zig";
import ComptimeReturningType from "!!raw-loader!./24.comptime-returning-type.zig";
import ComptimeTypeinfo from "!!raw-loader!./24.comptime-typeinfo.zig";
import ComptimeType from "!!raw-loader!./24.comptime-type.zig";
import ComptimeReturnStruct from "!!raw-loader!./24.comptime-return-struct.zig";
import ComptimeAnytype from "!!raw-loader!./24.comptime-anytype.zig";
import ComptimeConcatRepeat from "!!raw-loader!./24.comptime-concat-repeat.zig";
# Comptime
Blocks of code may be forcibly executed at compile time using the
[`comptime`](https://ziglang.org/documentation/master/#comptime) keyword. In
this example, the variables x and y are equivalent.
<CodeBlock language="zig">{ComptimeBlocks}</CodeBlock>
Integer literals are of the type `comptime_int`. These are special in that they
have no size (they cannot be used at runtime!), and they have arbitrary
precision. `comptime_int` values coerce to any integer type that can hold them.
They also coerce to floats. Character literals are of this type.
<CodeBlock language="zig">{ComptimeInts}</CodeBlock>
`comptime_float` is also available, which internally is an `f128`. These cannot
be coerced to integers, even if they hold an integer value.
Types in Zig are values of the type `type`. These are available at compile time.
We have previously encountered them by checking
[`@TypeOf`](https://ziglang.org/documentation/master/#TypeOf) and comparing with
other types, but we can do more.
<CodeBlock language="zig">{ComptimeTypeBranching}</CodeBlock>
Function parameters in Zig can be tagged as being
[`comptime`](https://ziglang.org/documentation/master/#comptime). This means
that the value passed to that function parameter must be known at compile time.
Let's make a function that returns a type. Notice how this function is
PascalCase, as it returns a type.
<CodeBlock language="zig">{ComptimeReturningType}</CodeBlock>
We can reflect upon types using the built-in
[`@typeInfo`](https://ziglang.org/documentation/master/#typeInfo), which takes
in a `type` and returns a tagged union. This tagged union type can be found in
[`std.builtin.Type`](https://ziglang.org/documentation/master/std/#std.builtin.Type)
(info on how to make use of imports and std later).
<CodeBlock language="zig">{ComptimeTypeinfo}</CodeBlock>
We can use the [`@Type`](https://ziglang.org/documentation/master/#Type)
function to create a type from a
[`@typeInfo`](https://ziglang.org/documentation/master/#typeInfo).
[`@Type`](https://ziglang.org/documentation/master/#Type) is implemented for
most types but is notably unimplemented for enums, unions, functions, and
structs.
Here anonymous struct syntax is used with `.{}`, because the `T` in `T{}` can be
inferred. Anonymous structs will be covered in detail later. In this example we
will get a compile error if the `Int` tag isn't set.
<CodeBlock language="zig">{ComptimeType}</CodeBlock>
Returning a struct type is how you make generic data structures in Zig. The
usage of [`@This`](https://ziglang.org/documentation/master/#This) is required
here, which gets the type of the innermost struct, union, or enum. Here
[`std.mem.eql`](https://ziglang.org/documentation/master/std/#std;mem.eql) is
also used which compares two slices.
<CodeBlock language="zig">{ComptimeReturnStruct}</CodeBlock>
The types of function parameters can also be inferred by using `anytype` in
place of a type. [`@TypeOf`](https://ziglang.org/documentation/master/#TypeOf)
can then be used on the parameter.
<CodeBlock language="zig">{ComptimeAnytype}</CodeBlock>
Comptime also introduces the operators `++` and `**` for concatenating and
repeating arrays and slices. These operators do not work at runtime.
<CodeBlock language="zig">{ComptimeConcatRepeat}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/16.struct.zig | const Vec3 = struct { x: f32, y: f32, z: f32 };
test "struct usage" {
const my_vector = Vec3{
.x = 0,
.y = 100,
.z = 50,
};
_ = my_vector;
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/31-imports.md | ---
pagination_next: standard-library/allocators
---
# Imports
The built-in function
[`@import`](https://ziglang.org/documentation/master/#import) takes in a file,
and gives you a struct type based on that file. All declarations labelled as
`pub` (for public) will end up in this struct type, ready for use.
`@import("std")` is a special case in the compiler, and gives you access to the
standard library. Other
[`@import`](https://ziglang.org/documentation/master/#import)s will take in a
file path, or a package name (more on packages in a later chapter).
We will explore more of the standard library in later chapters.
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/30.vectors-splat-scalar.zig | // hide-start
const expect = @import("std").testing.expect;
const meta = @import("std").meta;
//hide-end
test "vector * scalar" {
const x: @Vector(3, f32) = .{ 12.5, 37.5, 2.5 };
const y = x * @as(@Vector(3, f32), @splat(2));
try expect(meta.eql(y, @Vector(3, f32){ 25, 75, 5 }));
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/16.struct-defaults.zig | const Vec4 = struct { x: f32 = 0, y: f32 = 0, z: f32 = 0, w: f32 = 0 };
test "struct defaults" {
const my_vector = Vec4{
.x = 25,
.y = -50,
};
_ = my_vector;
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/19-floats.mdx | import CodeBlock from "@theme/CodeBlock";
import FloatsWidening from "!!raw-loader!./19.floats-widening.zig";
import FloatsLiterals from "!!raw-loader!./19.floats-literals.zig";
import FloatsHexUnderscores from "!!raw-loader!./19.floats-hex-underscores.zig";
import FloatsConversion from "!!raw-loader!./19.floats-conversion.zig";
# Floats
Zig's floats are strictly IEEE-compliant unless
[`@setFloatMode(.Optimized)`](https://ziglang.org/documentation/master/#setFloatMode)
is used, which is equivalent to GCC's `-ffast-math`. Floats coerce to larger
float types.
<CodeBlock language="zig">{FloatsWidening}</CodeBlock>
Floats support multiple kinds of literal.
<CodeBlock language="zig">{FloatsLiterals}</CodeBlock>
Underscores may also be placed between digits.
<CodeBlock language="zig">{FloatsHexUnderscores}</CodeBlock>
Integers and floats may be converted using the built-in functions
[`@floatFromInt`](https://ziglang.org/documentation/0.12.0/#floatFromInt) and
[`@intFromFloat`](https://ziglang.org/documentation/0.12.0/#intFromFloat).
[`@floatFromInt`](https://ziglang.org/documentation/0.12.0/#floatFromInt) is
always safe, whereas
[`@intFromFloat`](https://ziglang.org/documentation/0.12.0/#intFromFloat) is
detectable illegal behaviour if the float value cannot fit in the integer
destination type.
<CodeBlock language="zig">{FloatsConversion}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/08.error-set-merge.zig | const A = error{ NotDir, PathNotFound };
const B = error{ OutOfMemory, PathNotFound };
const C = A || B;
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/24.comptime-returning-type.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
fn Matrix(
comptime T: type,
comptime width: comptime_int,
comptime height: comptime_int,
) type {
return [height][width]T;
}
test "returning a type" {
try expect(Matrix(f32, 4, 4) == [4][4]f32);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/18.integer-widening.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "integer widening" {
const a: u8 = 250;
const b: u16 = a;
const c: u32 = b;
try expect(c == a);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/16-structs.mdx | import CodeBlock from "@theme/CodeBlock";
import Struct from "!!raw-loader!./16.struct.zig";
import StructDefaults from "!!raw-loader!./16.struct-defaults.zig";
import StructDeclarations from "!!raw-loader!./16.struct-declarations.zig";
# Structs
Structs are Zig's most common kind of composite data type, allowing you to
define types that can store a fixed set of named fields. Zig gives no guarantees
about the in-memory order of fields in a struct or its size. Like arrays,
structs are also neatly constructed with `T{}` syntax. Here is an example of
declaring and filling a struct.
<CodeBlock language="zig">{Struct}</CodeBlock>
Struct fields cannot be implicitly uninitialised:
```zig
test "missing struct field" {
const my_vector = Vec3{
.x = 0,
.z = 50,
};
_ = my_vector;
}
```
```
error: missing field: 'y'
const my_vector = Vec3{
^
```
Fields may be given defaults:
<CodeBlock language="zig">{StructDefaults}</CodeBlock>
Like enums, structs may also contain functions and declarations.
Structs have the unique property that when given a pointer to a struct, one
level of dereferencing is done automatically when accessing fields. Notice how,
in this example, `self.x` and `self.y` are accessed in the swap function without
needing to dereference the self pointer.
<CodeBlock language="zig">{StructDeclarations}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/30.vectors-indexing.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "vector indexing" {
const x: @Vector(4, u8) = .{ 255, 0, 255, 0 };
try expect(x[0] == 255);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/28.anonymous-structs-fully-anonymous.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "fully anonymous struct" {
try dump(.{
.int = @as(u32, 1234),
.float = @as(f64, 12.34),
.b = true,
.s = "hi",
});
}
fn dump(args: anytype) !void {
try expect(args.int == 1234);
try expect(args.float == 12.34);
try expect(args.b);
try expect(args.s[0] == 'h');
try expect(args.s[1] == 'i');
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/19.floats-hex-underscores.zig | const lightspeed: f64 = 299_792_458.000_000;
const nanosecond: f64 = 0.000_000_001;
const more_hex: f64 = 0x1234_5678.9ABC_CDEFp-10;
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/03.if-expression.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "if statement expression" {
const a = true;
var x: u16 = 0;
x += if (a) 1 else 2;
try expect(x == 1);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/23.optionals-find.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "optional" {
var found_index: ?usize = null;
const data = [_]i32{ 1, 2, 3, 4, 5, 6, 7, 8, 12 };
for (data, 0..) |v, i| {
if (v == 10) found_index = i;
}
try expect(found_index == null);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/05.for.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "for" {
//character literals are equivalent to integer literals
const string = [_]u8{ 'a', 'b', 'c' };
for (string, 0..) |character, index| {
_ = character;
_ = index;
}
for (string) |character| {
_ = character;
}
for (string, 0..) |_, index| {
_ = index;
}
for (string) |_| {}
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/08-errors.mdx | import CodeBlock from "@theme/CodeBlock";
import ErrorSet from "!!raw-loader!./08.error-set.zig";
import ErrorSetCoercion from "!!raw-loader!./08.error-set-coercion.zig";
import ErrorUnion from "!!raw-loader!./08.error-union.zig";
import ErrorPayloadCapture from "!!raw-loader!./08.error-payload-capture.zig";
import ErrorTry from "!!raw-loader!./08.error-try.zig";
import Errdefer from "!!raw-loader!./08.errdefer.zig";
import ErrorSetInferred from "!!raw-loader!./08.error-set-inferred.zig";
import ErrorSetMerge from "!!raw-loader!./08.error-set-merge.zig";
# Errors
An error set is like an enum (details on Zig's enums later), where each error in
the set is a value. There are no exceptions in Zig; errors are values. Let's
create an error set.
<CodeBlock language="zig">{ErrorSet}</CodeBlock>
Error sets coerce to their supersets.
<CodeBlock language="zig">{ErrorSetCoercion}</CodeBlock>
An error set type and another type can be combined with the `!` operator to form
an error union type. Values of these types may be an error value or a value of
the other type.
Let's create a value of an error union type. Here
[`catch`](https://ziglang.org/documentation/master/#catch) is used, which is
followed by an expression which is evaluated when the value preceding it is an
error. The catch here is used to provide a fallback value, but could instead be
a [`noreturn`](https://ziglang.org/documentation/master/#noreturn) - the type of
`return`, `while (true)` and others.
<CodeBlock language="zig">{ErrorUnion}</CodeBlock>
Functions often return error unions. Here's one using a catch, where the `|err|`
syntax receives the value of the error. This is called **payload capturing**,
and is used similarly in many places. We'll talk about it in more detail later
in the chapter. Side note: some languages use similar syntax for lambdas - this
is not true for Zig.
<CodeBlock language="zig">{ErrorPayloadCapture}</CodeBlock>
`try x` is a shortcut for `x catch |err| return err`, and is commonly used where
handling an error isn't appropriate. Zig's
[`try`](https://ziglang.org/documentation/master/#try) and
[`catch`](https://ziglang.org/documentation/master/#catch) are unrelated to
try-catch in other languages.
<CodeBlock language="zig">{ErrorTry}</CodeBlock>
[`errdefer`](https://ziglang.org/documentation/master/#errdefer) works like
[`defer`](https://ziglang.org/documentation/master/#defer), but only executing
when the function is returned from with an error inside of the
[`errdefer`](https://ziglang.org/documentation/master/#errdefer)'s block.
<CodeBlock language="zig">{Errdefer}</CodeBlock>
Error unions returned from a function can have their error sets inferred by not
having an explicit error set. This inferred error set contains all possible
errors that the function may return.
<CodeBlock language="zig">{ErrorSetInferred}</CodeBlock>
Error sets can be merged.
<CodeBlock language="zig">{ErrorSetMerge}</CodeBlock>
`anyerror` is the global error set, which due to being the superset of all error
sets, can have an error from any set coerced to it. Its usage should be
generally avoided.
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/15.enum-methods.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
const Suit = enum {
clubs,
spades,
diamonds,
hearts,
pub fn isClubs(self: Suit) bool {
return self == Suit.clubs;
}
};
test "enum method" {
try expect(Suit.spades.isClubs() == Suit.isClubs(.spades));
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/30.vectors-add.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
const meta = @import("std").meta;
test "vector add" {
const x: @Vector(4, f32) = .{ 1, -10, 20, -1 };
const y: @Vector(4, f32) = .{ 2, 10, 0, 1 };
const z = x + y;
try expect(meta.eql(z, @Vector(4, f32){ 3, 0, 20, 0 }));
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/09.switch-statement.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "switch statement" {
var x: i8 = 10;
switch (x) {
-1...1 => {
x = -x;
},
10, 100 => {
//special considerations must be made
//when dividing signed integers
x = @divExact(x, 10);
},
else => {},
}
try expect(x == 1);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/04.while-continue-expression.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "while with continue expression" {
var sum: u8 = 0;
var i: u8 = 1;
while (i <= 10) : (i += 1) {
sum += i;
}
try expect(sum == 55);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/05-for-loops.mdx | import CodeBlock from "@theme/CodeBlock";
import For from "!!raw-loader!./05.for.zig";
# For loops
For loops are used to iterate over arrays (and other types, to be discussed
later). For loops follow this syntax. Like while, for loops can use `break` and
`continue`. Here, we've had to assign values to `_`, as Zig does not allow us to
have unused values.
<CodeBlock language="zig">{For}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/03.expect.zig | const expect = @import("std").testing.expect;
test "if statement" {
const a = true;
var x: u16 = 0;
if (a) {
x += 1;
} else {
x += 2;
}
try expect(x == 1);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/24.comptime-blocks.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
fn fibonacci(n: u16) u16 {
if (n == 0 or n == 1) return n;
return fibonacci(n - 1) + fibonacci(n - 2);
}
test "comptime blocks" {
const x = comptime fibonacci(10);
const y = comptime blk: {
break :blk fibonacci(10);
};
try expect(y == 55);
try expect(x == 55);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/11.pointers.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
fn increment(num: *u8) void {
num.* += 1;
}
test "pointers" {
var x: u8 = 1;
increment(&x);
try expect(x == 2);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/25.payload-captures-switch-capture.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
const Info = union(enum) {
a: u32,
b: []const u8,
c,
d: u32,
};
test "switch capture" {
const b = Info{ .a = 10 };
const x = switch (b) {
.b => |str| blk: {
try expect(@TypeOf(str) == []const u8);
break :blk 1;
},
.c => 2,
//if these are of the same type, they
//may be inside the same capture group
.a, .d => |num| blk: {
try expect(@TypeOf(num) == u32);
break :blk num * 2;
},
};
try expect(x == 20);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/24.comptime-concat-repeat.zig | // hide-start
const expect = @import("std").testing.expect;
const eql = @import("std").mem.eql;
//hide-end
test "++" {
const x: [4]u8 = undefined;
const y = x[0..];
const a: [6]u8 = undefined;
const b = a[0..];
const new = y ++ b;
try expect(new.len == 10);
}
test "**" {
const pattern = [_]u8{ 0xCC, 0xAA };
const memory = pattern ** 3;
try expect(eql(u8, &memory, &[_]u8{ 0xCC, 0xAA, 0xCC, 0xAA, 0xCC, 0xAA }));
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/15.enum-declarations.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
const Mode = enum {
var count: u32 = 0;
on,
off,
};
test "hmm" {
Mode.count += 1;
try expect(Mode.count == 1);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/03-if.mdx | import CodeBlock from "@theme/CodeBlock";
import Expect from "!!raw-loader!./03.expect.zig";
import IfExpression from "!!raw-loader!./03.if-expression.zig";
# If Expressions
Zig's if statements accept `bool` values (i.e. `true` or `false`). Unlike languages
like C or Javascript, there are no values that implicitly coerce to bool values.
Here, we will introduce testing. Save the below code and compile + run it with
`zig test file-name.zig`. We will be using the
[`expect`](https://ziglang.org/documentation/master/std/#std.testing.expect)
function from the standard library, which will cause the test to fail if it's
given the value `false`. When a test fails, the error and stack trace will be
shown.
<CodeBlock language="zig">{Expect}</CodeBlock>
If statements also work as expressions.
<CodeBlock language="zig">{IfExpression}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/29.sentinel-termination-ptrcast.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "sentinel termination" {
const terminated = [3:0]u8{ 3, 2, 1 };
try expect(terminated.len == 3);
try expect(@as(*const [4]u8, @ptrCast(&terminated))[3] == 0);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/04.while-continue.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "while with continue" {
var sum: u8 = 0;
var i: u8 = 0;
while (i <= 3) : (i += 1) {
if (i == 2) continue;
sum += i;
}
try expect(sum == 4);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/06.functions.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
fn addFive(x: u32) u32 {
return x + 5;
}
test "function" {
const y = addFive(0);
try expect(@TypeOf(y) == u32);
try expect(y == 5);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/07-defer.mdx | import CodeBlock from "@theme/CodeBlock";
import Defer from "!!raw-loader!./07.defer.zig";
import DeferMulti from "!!raw-loader!./07.defer-multi.zig";
# Defer
Defer is used to execute a statement while exiting the current block.
<CodeBlock language="zig">{Defer}</CodeBlock>
When there are multiple defers in a single block, they are executed in reverse
order.
<CodeBlock language="zig">{DeferMulti}</CodeBlock>
Defer is useful to ensure that resources are cleaned up when they are no longer needed.
Instead of needing to remember to manually free up the resource,
you can add a defer statement right next to the statement that allocates the resource.
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/25.payload-captures-while-error-union.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
var numbers_left2: u32 = undefined;
fn eventuallyErrorSequence() !u32 {
return if (numbers_left2 == 0) error.ReachedZero else blk: {
numbers_left2 -= 1;
break :blk numbers_left2;
};
}
test "while error union capture" {
var sum: u32 = 0;
numbers_left2 = 3;
while (eventuallyErrorSequence()) |value| {
sum += value;
} else |err| {
try expect(err == error.ReachedZero);
}
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/25-payload-captures.mdx | import CodeBlock from "@theme/CodeBlock";
import PayloadCapturesOptionalIf from "!!raw-loader!./25.payload-captures-optional-if.zig";
import PayloadCapturesErrorUnionIf from "!!raw-loader!./25.payload-captures-error-union-if.zig";
import PayloadCapturesWhileOptional from "!!raw-loader!./25.payload-captures-while-optional.zig";
import PayloadCapturesWhileErrorUnion from "!!raw-loader!./25.payload-captures-while-error-union.zig";
import PayloadCapturesForCapture from "!!raw-loader!./25.payload-captures-for-capture.zig";
import PayloadCapturesSwitchCapture from "!!raw-loader!./25.payload-captures-switch-capture.zig";
import PayloadCapturesForPointerCapture from "!!raw-loader!./25.payload-captures-for-pointer-capture.zig";
# Payload Captures
Payload captures use the syntax `|value|` and appear in many places, some of
which we've seen already. Wherever they appear, they are used to "capture" the
value from something.
With if statements and optionals.
<CodeBlock language="zig">{PayloadCapturesOptionalIf}</CodeBlock>
With if statements and error unions. The else with the error capture is required
here.
<CodeBlock language="zig">{PayloadCapturesErrorUnionIf}</CodeBlock>
With while loops and optionals. This may have an else block.
<CodeBlock language="zig">{PayloadCapturesWhileOptional}</CodeBlock>
With while loops and error unions. The else with the error capture is required
here.
<CodeBlock language="zig">{PayloadCapturesWhileErrorUnion}</CodeBlock>
For loops.
<CodeBlock language="zig">{PayloadCapturesForCapture}</CodeBlock>
Switch cases on tagged unions.
<CodeBlock language="zig">{PayloadCapturesSwitchCapture}</CodeBlock>
As we saw in the Union and Optional sections above, values captured with the
`|val|` syntax are immutable (similar to function arguments), but we can use
pointer capture to modify the original values. This captures the values as
pointers that are themselves still immutable, but because the value is now a
pointer, we can modify the original value by dereferencing it:
<CodeBlock language="zig">{PayloadCapturesForPointerCapture}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/16.struct-declarations.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
const Stuff = struct {
x: i32,
y: i32,
fn swap(self: *Stuff) void {
const tmp = self.x;
self.x = self.y;
self.y = tmp;
}
};
test "automatic dereference" {
var thing = Stuff{ .x = 10, .y = 20 };
thing.swap();
try expect(thing.x == 20);
try expect(thing.y == 10);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/18.integer-safe-overflow.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "well defined overflow" {
var a: u8 = 255;
a +%= 1;
try expect(a == 0);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/08.error-payload-capture.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
fn failingFunction() error{Oops}!void {
return error.Oops;
}
test "returning an error" {
failingFunction() catch |err| {
try expect(err == error.Oops);
return;
};
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/15.enum-ordinal-override.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
const Value2 = enum(u32) {
hundred = 100,
thousand = 1000,
million = 1000000,
next,
};
test "set enum ordinal value" {
try expect(@intFromEnum(Value2.hundred) == 100);
try expect(@intFromEnum(Value2.thousand) == 1000);
try expect(@intFromEnum(Value2.million) == 1000000);
try expect(@intFromEnum(Value2.next) == 1000001);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/08.error-union.zig | // hide-start
const expect = @import("std").testing.expect;
const FileOpenError = error{
AccessDenied,
OutOfMemory,
FileNotFound,
};
const AllocationError = error{OutOfMemory};
// hide-end
test "error union" {
const maybe_error: AllocationError!u16 = 10;
const no_error = maybe_error catch 0;
try expect(@TypeOf(no_error) == u16);
try expect(no_error == 10);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/04.while.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "while" {
var i: u8 = 2;
while (i < 100) {
i *= 2;
}
try expect(i == 128);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/15.enum-ordinal.zig | // hide-start
const expect = @import("std").testing.expect;
const Value = enum(u2) { zero, one, two };
// hide-end
test "enum ordinal value" {
try expect(@intFromEnum(Value.zero) == 0);
try expect(@intFromEnum(Value.one) == 1);
try expect(@intFromEnum(Value.two) == 2);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/29.sentinel-termination-coercion.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "coercion" {
const a: [*:0]u8 = undefined;
const b: [*]u8 = a;
const c: [5:0]u8 = undefined;
const d: [5]u8 = c;
const e: [:0]f32 = undefined;
const f: []f32 = e;
_ = .{ b, d, f }; //ignore unused
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/02-arrays.md | # Arrays
Arrays are denoted by `[N]T`, where `N` is the number of elements in the array
and `T` is the type of those elements (i.e., the array's child type).
For array literals, `N` may be replaced by `_` to infer the size of the array.
```zig
const a = [5]u8{ 'h', 'e', 'l', 'l', 'o' };
const b = [_]u8{ 'w', 'o', 'r', 'l', 'd' };
```
To get the size of an array, simply access the array's `len` field.
```zig
const array = [_]u8{ 'h', 'e', 'l', 'l', 'o' };
const length = array.len; // 5
```
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/19.floats-widening.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "float widening" {
const a: f16 = 0;
const b: f32 = a;
const c: f128 = b;
try expect(c == @as(f128, a));
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/06.functions-recursion.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
fn fibonacci(n: u16) u16 {
if (n == 0 or n == 1) return n;
return fibonacci(n - 1) + fibonacci(n - 2);
}
test "function recursion" {
const x = fibonacci(10);
try expect(x == 55);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/17-unions.mdx | import CodeBlock from "@theme/CodeBlock";
import TaggedUnion from "!!raw-loader!./17.union-tagged.zig";
# Unions
Zig's unions allow you to define types that store one value of many possible
typed fields; only one field may be active at one time.
Bare union types do not have a guaranteed memory layout. Because of this, bare
unions cannot be used to reinterpret memory. Accessing a field in a union that
is not active is detectable illegal behaviour.
```zig
const Result = union {
int: i64,
float: f64,
bool: bool,
};
test "simple union" {
var result = Result{ .int = 1234 };
result.float = 12.34;
}
```
```
test "simple union"...access of inactive union field
.\tests.zig:342:12: 0x7ff62c89244a in test "simple union" (test.obj)
result.float = 12.34;
^
```
Tagged unions are unions that use an enum to detect which field is active. Here
we make use of payload capturing again, to switch on the tag type of a union
while also capturing the value it contains. Here we use a _pointer capture_;
captured values are immutable, but with the `|*value|` syntax, we can capture a
pointer to the values instead of the values themselves. This allows us to use
dereferencing to mutate the original value.
<CodeBlock language="zig">{TaggedUnion}</CodeBlock>
The tag type of a tagged union can also be inferred. This is equivalent to the
Tagged type above.
```zig
const Tagged = union(enum) { a: u8, b: f32, c: bool };
```
`void` member types can have their type omitted from the syntax. Here, none is
of type `void`.
```zig
const Tagged2 = union(enum) { a: u8, b: f32, c: bool, none };
```
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/01-assignment.mdx | ---
pagination_prev: getting-started/running-tests
---
import CodeBlock from "@theme/CodeBlock";
import Assignment from "!!raw-loader!./01.assignment.zig";
import Undefined from "!!raw-loader!./01.undefined.zig";
# Assignment
Value assignment has the following syntax:
`(const|var) identifier[: type] = value`.
- `const` indicates that `identifier` is a **constant** that stores an immutable
value.
- `var` indicates that `identifier` is a **variable** that stores a mutable
value.
- `: type` is a type annotation for `identifier`, and may be omitted if the data
type of `value` can be inferred.
<CodeBlock language="zig">{Assignment}</CodeBlock>
Constants and variables _must_ have a value. If no known value can be given, the
[`undefined`](https://ziglang.org/documentation/master/#undefined) value, which
coerces to any type, may be used as long as a type annotation is provided.
<CodeBlock language="zig">{Undefined}</CodeBlock>
Where possible, `const` values are preferred over `var` values.
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/09.switch-expression.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "switch expression" {
var x: i8 = 10;
x = switch (x) {
-1...1 => -x,
10, 100 => @divExact(x, 10),
else => x,
};
try expect(x == 1);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/23.optionals-orelse.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "orelse" {
const a: ?f32 = null;
const fallback_value: f32 = 0;
const b = a orelse fallback_value;
try expect(b == 0);
try expect(@TypeOf(b) == f32);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/04-while-loops.mdx | import CodeBlock from "@theme/CodeBlock";
import While from "!!raw-loader!./04.while.zig";
import WhileContinueExpression from "!!raw-loader!./04.while-continue-expression.zig";
import WhileContinue from "!!raw-loader!./04.while-continue.zig";
import WhileBreak from "!!raw-loader!./04.while-break.zig";
# While loops
Zig's while loop has three parts - a condition, a block and a continue
expression.
Without a continue expression.
<CodeBlock language="zig">{While}</CodeBlock>
With a continue expression.
<CodeBlock language="zig">{WhileContinueExpression}</CodeBlock>
With a `continue`.
<CodeBlock language="zig">{WhileContinue}</CodeBlock>
With a `break`.
<CodeBlock language="zig">{WhileBreak}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/23.optionals-if-payload.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "if optional payload capture" {
const a: ?i32 = 5;
if (a != null) {
const value = a.?;
_ = value;
}
var b: ?i32 = 5;
if (b) |*value| {
value.* += 1;
}
try expect(b.? == 6);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/25.payload-captures-for-pointer-capture.zig | // hide-start
const expect = @import("std").testing.expect;
const eql = @import("std").mem.eql;
//hide-end
test "for with pointer capture" {
var data = [_]u8{ 1, 2, 3 };
for (&data) |*byte| byte.* += 1;
try expect(eql(u8, &data, &[_]u8{ 2, 3, 4 }));
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/29-sentinel-termination.mdx | import CodeBlock from "@theme/CodeBlock";
import SentinelTerminationPtrcast from "!!raw-loader!./29.sentinel-termination-ptrcast.zig";
import SentinelTerminationStringLiteral from "!!raw-loader!./29.sentinel-termination-string-literal.zig";
import SentinelTerminationCString from "!!raw-loader!./29.sentinel-termination-c-string.zig";
import SentinelTerminationCoercion from "!!raw-loader!./29.sentinel-termination-coercion.zig";
import SentinelTerminationSlicing from "!!raw-loader!./29.sentinel-termination-slicing.zig";
# Sentinel Termination
Arrays, slices and many pointers may be terminated by a value of their child
type. This is known as sentinel termination. These follow the syntax `[N:t]T`,
`[:t]T`, and `[*:t]T`, where `t` is a value of the child type `T`.
An example of a sentinel terminated array. The built-in
[`@ptrCast`](https://ziglang.org/documentation/master/#ptrCast) is used to
perform an unsafe type conversion. This shows us that the last element of the
array is followed by a 0 byte.
<CodeBlock language="zig">{SentinelTerminationPtrcast}</CodeBlock>
The types of string literals is `*const [N:0]u8`, where N is the length of the
string. This allows string literals to coerce to sentinel terminated slices, and
sentinel terminated many pointers. Note: string literals are UTF-8 encoded.
<CodeBlock language="zig">{SentinelTerminationStringLiteral}</CodeBlock>
`[*:0]u8` and `[*:0]const u8` perfectly model C's strings.
<CodeBlock language="zig">{SentinelTerminationCString}</CodeBlock>
Sentinel terminated types coerce to their non-sentinel-terminated counterparts.
<CodeBlock language="zig">{SentinelTerminationCoercion}</CodeBlock>
Sentinel terminated slicing is provided which can be used to create a sentinel
terminated slice with the syntax `x[n..m:t]`, where `t` is the terminator value.
Doing this is an assertion from the programmer that the memory is terminated
where it should be - getting this wrong is detectable illegal behaviour.
<CodeBlock language="zig">{SentinelTerminationSlicing}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/23.optionals-while-capture.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
var numbers_left: u32 = 4;
fn eventuallyNullSequence() ?u32 {
if (numbers_left == 0) return null;
numbers_left -= 1;
return numbers_left;
}
test "while null capture" {
var sum: u32 = 0;
while (eventuallyNullSequence()) |value| {
sum += value;
}
try expect(sum == 6); // 3 + 2 + 1
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/25.payload-captures-for-capture.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "for capture" {
const x = [_]i8{ 1, 5, 120, -5 };
for (x) |v| try expect(@TypeOf(v) == i8);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/06-functions.mdx | import CodeBlock from "@theme/CodeBlock";
import Functions from "!!raw-loader!./06.functions.zig";
import FunctionsRecursion from "!!raw-loader!./06.functions-recursion.zig";
# Functions
**All function arguments are immutable** - if a copy is desired the user must
explicitly make one. Unlike variables, which are snake_case, functions are
camelCase. Here's an example of declaring and calling a simple function.
<CodeBlock language="zig">{Functions}</CodeBlock>
Recursion is allowed:
<CodeBlock language="zig">{FunctionsRecursion}</CodeBlock>
When recursion happens, the compiler is no longer able to work out the maximum
stack size, which may result in unsafe behaviour - a stack overflow. Details on
how to achieve safe recursion will be covered in future.
Values can be ignored using `_` instead of a variable or const declaration. This
does not work at the global scope (i.e. it only works inside functions and
blocks) and is useful for ignoring the values returned from functions if you do
not need them.
```zig
_ = 10;
```
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/08.error-set-coercion.zig | // hide-start
const expect = @import("std").testing.expect;
const FileOpenError = error{
AccessDenied,
OutOfMemory,
FileNotFound,
};
// hide-end
const AllocationError = error{OutOfMemory};
test "coerce error from a subset to a superset" {
const err: FileOpenError = AllocationError.OutOfMemory;
try expect(err == FileOpenError.OutOfMemory);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/14.slices-2.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "slices 2" {
const array = [_]u8{ 1, 2, 3, 4, 5 };
const slice = array[0..3];
try expect(@TypeOf(slice) == *const [3]u8);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/08.errdefer.zig | // hide-start
const expect = @import("std").testing.expect;
fn failingFunction() error{Oops}!void {
return error.Oops;
}
//hide-end
var problems: u32 = 98;
fn failFnCounter() error{Oops}!void {
errdefer problems += 1;
try failingFunction();
}
test "errdefer" {
failFnCounter() catch |err| {
try expect(err == error.Oops);
try expect(problems == 99);
return;
};
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/24.comptime-type.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
fn GetBiggerInt(comptime T: type) type {
return @Type(.{
.Int = .{
.bits = @typeInfo(T).Int.bits + 1,
.signedness = @typeInfo(T).Int.signedness,
},
});
}
test "@Type" {
try expect(GetBiggerInt(u8) == u9);
try expect(GetBiggerInt(i31) == i32);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/24.comptime-anytype.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
fn plusOne(x: anytype) @TypeOf(x) {
return x + 1;
}
test "inferred function parameter" {
try expect(plusOne(@as(u32, 1)) == 2);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/28-anonymous-structs.mdx | import CodeBlock from "@theme/CodeBlock";
import AnonymousStructsLiteral from "!!raw-loader!./28.anonymous-structs-literal.zig";
import AnonymousStructsFullyAnonymous from "!!raw-loader!./28.anonymous-structs-fully-anonymous.zig";
import AnonymousStructsTuple from "!!raw-loader!./28.anonymous-structs-tuple.zig";
# Anonymous Structs
The struct type may be omitted from a struct literal. These literals may coerce
to other struct types.
<CodeBlock language="zig">{AnonymousStructsLiteral}</CodeBlock>
Anonymous structs may be completely anonymous i.e. without being coerced to
another struct type.
<CodeBlock language="zig">{AnonymousStructsFullyAnonymous}</CodeBlock>
{/* TODO: mention tuple slicing when it's implemented */}
Anonymous structs without field names may be created and are referred to as
**tuples**. These have many of the properties that arrays do; tuples can be
iterated over, indexed, can be used with the `++` and `**` operators, and have a
len field. Internally, these have numbered field names starting at `"0"`, which
may be accessed with the special syntax `@"0"` which acts as an escape for the
syntax - things inside `@""` are always recognised as identifiers.
An `inline` loop must be used to iterate over the tuple here, as the type of
each tuple field may differ.
<CodeBlock language="zig">{AnonymousStructsTuple}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/24.comptime-type-branching.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "branching on types" {
const a = 5;
const b: if (a < 10) f32 else i32 = 5;
try expect(b == 5);
try expect(@TypeOf(b) == f32);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/01.assignment.zig | const constant: i32 = 5; // signed 32-bit constant
var variable: u32 = 5000; // unsigned 32-bit variable
// @as performs an explicit type coercion
const inferred_constant = @as(i32, 5);
var inferred_variable = @as(u32, 5000);
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/28.anonymous-structs-literal.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "anonymous struct literal" {
const Point = struct { x: i32, y: i32 };
const pt: Point = .{
.x = 13,
.y = 67,
};
try expect(pt.x == 13);
try expect(pt.y == 67);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/28.anonymous-structs-tuple.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "tuple" {
const values = .{
@as(u32, 1234),
@as(f64, 12.34),
true,
"hi",
} ++ .{false} ** 2;
try expect(values[0] == 1234);
try expect(values[4] == false);
inline for (values, 0..) |v, i| {
if (i != 2) continue;
try expect(v);
}
try expect(values.len == 6);
try expect(values.@"3"[0] == 'h');
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/20-labelled-blocks.md | # Labelled Blocks
Blocks in Zig are expressions and can be given labels, which are used to yield
values. Here, we are using a label called `blk`. Blocks yield values, meaning
they can be used in place of a value. The value of an empty block `{}` is a
value of the type `void`.
```zig
test "labelled blocks" {
const count = blk: {
var sum: u32 = 0;
var i: u32 = 0;
while (i < 10) : (i += 1) sum += i;
break :blk sum;
};
try expect(count == 45);
try expect(@TypeOf(count) == u32);
}
```
This can be seen as being equivalent to C's `i++`.
<!--no_test-->
```zig
blk: {
const tmp = i;
i += 1;
break :blk tmp;
}
```
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/22-loops-as-expressions.md | # Loops as Expressions
Like `return`, `break` accepts a value. This can be used to yield a value from a
loop. Loops in Zig also have an `else` branch, which is evaluated when the loop
is not exited with a `break`.
```zig
fn rangeHasNumber(begin: usize, end: usize, number: usize) bool {
var i = begin;
return while (i < end) : (i += 1) {
if (i == number) {
break true;
}
} else false;
}
test "while loop expression" {
try expect(rangeHasNumber(0, 10, 3));
}
```
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/04.while-break.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "while with break" {
var sum: u8 = 0;
var i: u8 = 0;
while (i <= 3) : (i += 1) {
if (i == 2) break;
sum += i;
}
try expect(sum == 1);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/19.floats-literals.zig | const floating_point: f64 = 123.0E+77;
const another_float: f64 = 123.0;
const yet_another: f64 = 123.0e+77;
const hex_floating_point: f64 = 0x103.70p-5;
const another_hex_float: f64 = 0x103.70;
const yet_another_hex_float: f64 = 0x103.70P-5;
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/12-pointer-sized-integers.md | # Pointer Sized Integers
`usize` and `isize` are given as unsigned and signed integers which are the same
size as pointers.
```zig
test "usize" {
try expect(@sizeOf(usize) == @sizeOf(*u8));
try expect(@sizeOf(isize) == @sizeOf(*u8));
}
```
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/09-switch.mdx | import CodeBlock from "@theme/CodeBlock";
import SwitchStatement from "!!raw-loader!./09.switch-statement.zig";
import SwitchExpression from "!!raw-loader!./09.switch-expression.zig";
# Switch
Zig's `switch` works as both a statement and an expression. The types of all
branches must coerce to the type which is being switched upon. All possible
values must have an associated branch - values cannot be left out. Cases cannot
fall through to other branches.
An example of a switch statement. The else is required to satisfy the
exhaustiveness of this switch.
<CodeBlock language="zig">{SwitchStatement}</CodeBlock>
Here is the former, but as a switch expression.
<CodeBlock language="zig">{SwitchExpression}</CodeBlock>
:::info
Now is the perfect time to use what you've learned and [solve a problem together](/posts/fizz-buzz).
:::
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/17.union-tagged.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
const Tag = enum { a, b, c };
const Tagged = union(Tag) { a: u8, b: f32, c: bool };
test "switch on tagged union" {
var value = Tagged{ .b = 1.5 };
switch (value) {
.a => |*byte| byte.* += 1,
.b => |*float| float.* *= 2,
.c => |*b| b.* = !b.*,
}
try expect(value.b == 3);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/25.payload-captures-while-optional.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "while optional" {
var i: ?u32 = 10;
while (i) |num| : (i.? -= 1) {
try expect(@TypeOf(num) == u32);
if (num == 1) {
i = null;
break;
}
}
try expect(i == null);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/30-vectors.mdx | import CodeBlock from "@theme/CodeBlock";
import VectorsAdd from "!!raw-loader!./30.vectors-add.zig";
import VectorsIndexing from "!!raw-loader!./30.vectors-indexing.zig";
import VectorsSplatScalar from "!!raw-loader!./30.vectors-splat-scalar.zig";
import VectorsLooping from "!!raw-loader!./30.vectors-looping.zig";
import VectorsCoercion from "!!raw-loader!./30.vectors-coercion.zig";
# Vectors
Zig provides vector types for SIMD. These are not to be conflated with vectors
in a mathematical sense, or vectors like C++'s std::vector (for this, see
"Arraylist" in chapter 2). Vectors may be created using the
[`@Type`](https://ziglang.org/documentation/master/#Type) built-in we used
earlier, and
[`std.meta.Vector`](https://ziglang.org/documentation/master/std/#std;meta.Vector)
provides a shorthand for this.
Vectors can only have child types of booleans, integers, floats and pointers.
Operations between vectors with the same child type and length can take place.
These operations are performed on each of the values in the
vector.[`std.meta.eql`](https://ziglang.org/documentation/master/std/#std;meta.eql)
is used here to check for equality between two vectors (also useful for other
types like structs).
<CodeBlock language="zig">{VectorsAdd}</CodeBlock>
Vectors are indexable.
<CodeBlock language="zig">{VectorsIndexing}</CodeBlock>
The built-in function
[`@splat`](https://ziglang.org/documentation/master/#splat) may be used to
construct a vector where all of the values are the same. Here we use it to
multiply a vector by a scalar.
<CodeBlock language="zig">{VectorsSplatScalar}</CodeBlock>
Vectors do not have a `len` field like arrays, but may still be looped over.
<CodeBlock language="zig">{VectorsLooping}</CodeBlock>
```zig
test "vector looping" {
const x = @Vector(4, u8){ 255, 0, 255, 0 };
var sum = blk: {
var tmp: u10 = 0;
var i: u8 = 0;
while (i < 4) : (i += 1) tmp += x[i];
break :blk tmp;
};
try expect(sum == 510);
}
```
Vectors coerce to their respective arrays.
<CodeBlock language="zig">{VectorsCoercion}</CodeBlock>
It is worth noting that using explicit vectors may result in slower software if
you do not make the right decisions - the compiler's auto-vectorisation is
fairly smart as-is.
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/29.sentinel-termination-slicing.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "sentinel terminated slicing" {
var x = [_:0]u8{255} ** 3;
const y = x[0..3 :0];
_ = y;
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/26-inline-loops.md | # Inline Loops
`inline` loops are unrolled, and allow some things to happen that only work at
compile time. Here we use a
[`for`](https://ziglang.org/documentation/master/#inline-for), but a
[`while`](https://ziglang.org/documentation/master/#inline-while) works
similarly.
```zig
test "inline for" {
const types = [_]type{ i32, f32, u8, bool };
var sum: usize = 0;
inline for (types) |T| sum += @sizeOf(T);
try expect(sum == 10);
}
```
Using these for performance reasons is inadvisable unless you've tested that
explicitly unrolling is faster; the compiler tends to make better decisions here
than you.
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/07.defer-multi.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
test "multi defer" {
var x: f32 = 5;
{
defer x += 2;
defer x /= 2;
}
try expect(x == 4.5);
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/10.switch-unreachable.zig | // hide-start
const expect = @import("std").testing.expect;
// hide-end
fn asciiToUpper(x: u8) u8 {
return switch (x) {
'a'...'z' => x + 'A' - 'a',
'A'...'Z' => x,
else => unreachable,
};
}
test "unreachable switch" {
try expect(asciiToUpper('a') == 'A');
try expect(asciiToUpper('A') == 'A');
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/10-runtime-safety.mdx | import CodeBlock from "@theme/CodeBlock";
import SwitchUnreachable from "!!raw-loader!./10.switch-unreachable.zig";
# Runtime Safety
Zig provides a level of safety, where problems may be found during execution.
Safety can be left on, or turned off. Zig has many cases of so-called
**detectable illegal behaviour**, meaning that illegal behaviour will be caught
(causing a panic) with safety on, but will result in undefined behaviour with
safety off. Users are strongly recommended to develop and test their software
with safety on, despite its speed penalties.
For example, runtime safety protects you from out of bounds indices.
```zig
test "out of bounds" {
const a = [3]u8{ 1, 2, 3 };
var index: u8 = 5;
const b = a[index];
_ = b;
_ = &index;
}
```
```
test "out of bounds"...index out of bounds
.\tests.zig:43:14: 0x7ff698cc1b82 in test "out of bounds" (test.obj)
const b = a[index];
^
```
The user may disable runtime safety for the current block using the built-in
function
[`@setRuntimeSafety`](https://ziglang.org/documentation/master/#setRuntimeSafety).
```zig
test "out of bounds, no safety" {
@setRuntimeSafety(false);
const a = [3]u8{ 1, 2, 3 };
var index: u8 = 5;
const b = a[index];
_ = b;
_ = &index;
}
```
Safety is off for some build modes (to be discussed later).
# Unreachable
[`unreachable`](https://ziglang.org/documentation/master/#unreachable) is an
assertion to the compiler that this statement will not be reached. It can tell
the compiler that a branch is impossible, which the optimiser can then take
advantage of. Reaching an
[`unreachable`](https://ziglang.org/documentation/master/#unreachable) is
detectable illegal behaviour.
As it is of the type
[`noreturn`](https://ziglang.org/documentation/master/#noreturn), it is
compatible with all other types. Here it coerces to u32.
```zig
test "unreachable" {
const x: i32 = 1;
const y: u32 = if (x == 2) 5 else unreachable;
_ = y;
}
```
```
test "unreachable"...reached unreachable code
.\tests.zig:211:39: 0x7ff7e29b2049 in test "unreachable" (test.obj)
const y: u32 = if (x == 2) 5 else unreachable;
^
```
Here is an unreachable being used in a switch.
<CodeBlock language="zig">{SwitchUnreachable}</CodeBlock>
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/29.sentinel-termination-c-string.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
test "C string" {
const c_string: [*:0]const u8 = "hello";
var array: [5]u8 = undefined;
var i: usize = 0;
while (c_string[i] != 0) : (i += 1) {
array[i] = c_string[i];
}
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/13-many-item-pointers.md | # Many-item Pointers
Sometimes, you may have a pointer to an unknown number of elements. `[*]T` is
the solution for this, which works like `*T` but also supports indexing syntax,
pointer arithmetic, and slicing. Unlike `*T`, it cannot point to a type that
does not have a known size. `*T` coerces to `[*]T`.
These many pointers may point to any amount of elements, including 0 and 1.
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/24.comptime-return-struct.zig | // hide-start
const expect = @import("std").testing.expect;
//hide-end
fn Vec(
comptime count: comptime_int,
comptime T: type,
) type {
return struct {
data: [count]T,
const Self = @This();
fn abs(self: Self) Self {
var tmp = Self{ .data = undefined };
for (self.data, 0..) |elem, i| {
tmp.data[i] = if (elem < 0)
-elem
else
elem;
}
return tmp;
}
fn init(data: [count]T) Self {
return Self{ .data = data };
}
};
}
const eql = @import("std").mem.eql;
test "generic vector" {
const x = Vec(3, f32).init([_]f32{ 10, -10, 5 });
const y = x.abs();
try expect(eql(f32, &y.data, &[_]f32{ 10, 10, 5 }));
}
|
0 | repos/zig.guide/website/versioned_docs/version-0.14 | repos/zig.guide/website/versioned_docs/version-0.14/01-language-basics/11-pointers.mdx | import CodeBlock from "@theme/CodeBlock";
import Pointers from "!!raw-loader!./11.pointers.zig";
# Pointers
Normal pointers in Zig cannot have 0 or null as a value. They follow the syntax
`*T`, where `T` is the child type.
Referencing is done with `&variable`, and dereferencing is done with
`variable.*`.
<CodeBlock language="zig">{Pointers}</CodeBlock>
Trying to set a `*T` to the value 0 is detectable illegal behaviour.
```zig
test "naughty pointer" {
var x: u16 = 0;
var y: *u8 = @ptrFromInt(x);
_ = y;
}
```
```
Test [23/126] test.naughty pointer... thread 21598 panic: cast causes pointer to be null
./test-c1.zig:252:18: 0x260a91 in test.naughty pointer (test)
var y: *u8 = @ptrFromInt(x);
^
```
Zig also has const pointers, which cannot be used to modify the referenced data.
Referencing a const variable will yield a const pointer.
```zig
test "const pointers" {
const x: u8 = 1;
var y = &x;
y.* += 1;
}
```
```
error: cannot assign to constant
y.* += 1;
^
```
A `*T` coerces to a `*const T`.
|
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