pub fn is_primitive(&self) -> bool {
        match *self {
            Integer(_) | Sym(_) | Approx(_) => true,
            _ => false,
        }
    }
/// Check if the expression is a primitive.
/// # Examples
/// ```
/// use symrs::sym::{Expr, Symbol};
///
/// assert_eq!(Expr::integer(1).is_primitive(), true);
/// assert_eq!(Expr::approximate(1).is_primitive(), true);
/// let x = Symbol::new("x");
/// assert_eq!((x + 1).is_primitive(), false);
/// ```
Check if the expression is a primitive.
Check if the expression is a primitive .
pub fn is_primitive(&self) -> bool {
        match *self {
            Integer(_) | Sym(_) | Approx(_) => true,
            _ => false,
        }
    }
pub fn is_primitive ( & self ) -> bool { match * self { Integer ( _ ) | Sym ( _ ) | Approx ( _ ) => true , _ => false , } }
Check if the expression is a primitive.
Check if the expression is a primitive .
&self
examples
```
use symrs::sym::{Expr, Symbol}.

assert_eq!(Expr::integer(1).is_primitive(), true);
assert_eq!(Expr::approximate(1).is_primitive(), true);
let x = Symbol::new("x");
assert_eq!((x + 1).is_primitive(), false);
```
` ` ` use symrs :: sym :: { Expr Symbol } . assert_eq! ( Expr :: integer ( 1 ) . is_primitive () true ) ; assert_eq! ( Expr :: approximate ( 1 ) . is_primitive () true ) ; let x = Symbol :: new ( " x " ) ; assert_eq! (( x + 1 ) . is_primitive () false ) ; ` ` `