I'm writing a grammar to recognise simple mathematical expressions. I have it working for English.

Now I want to expand the grammar to support i18n. Therefore, the digits, radix separator and so forth depend on the user's locale.

What is the best way to do this in ANTLR?

What I'm currently considering is something like this:

```
lexer grammar ExpressionLexer;

options {
    superClass = AbstractLexer;
}

DIGIT: . {isDigit(getText())}?;
// ... and so on for other tokens ...

```

```kotlin
abstract class AbstractLexer(input: CharStream, symbols: Symbols) extends Lexer(input) {
    fun isDigit(codePoint: Int): Boolean = symbols.isDigit(codePoint)
    // ... and so on for other tokens ...
}

```

Alternative approaches I am considering:

(b) I gather every possible digit and every possible separator in every possible locale, and jam all of those into the one grammar, and then check `isDigit` after that.

(c) I make a different lexer for every single numbering system and *somehow* align them all to emit the same token types in the same order, so they can be swapped in and out (sounds like it might be the most pure and correct solution? but not the most enjoyable.)

(And on a side tangent, how do people in European countries which use comma for the decimal separator deal with writing function calls with more than one parameter?)