On Tue, Jan 7, 2020 at 10:22 AM Tom Payne <twpa...@gmail.com> wrote:
>
> tl;dr How should I use named Unicode character classes in regexps?
>
> I'm trying to write a regular expression that matches Go identifiers, which
> start with a Unicode letter or underscore followed by zero or more Unicode
> letters, decimal digits, and/or underscores.
>
> Based on the regexp syntax, and the variables in the unicode package which
> mention the classes "Letter" and "Number, decimal digit", I was expecting to
> write something like:
>
> identiferRegexp :=
> regexp.MustCompile(`\A[[\p{Letter}]_][[\p{Letter}][\p{Number, decimal
> digit}]_]*\z`)
>
> However, this pattern does not compile, giving the error:
>
> regexp: Compile(`\A[[\p{Letter}]_][[\p{Letter}][\p{Number, decimal
> digit}]_]*\z`): error parsing regexp: invalid character class range:
> `\p{Letter}`
>
> Using the short name for character classes (L for Letter, Nd for Number,
> decimal digit) does work however:
>
> identiferRegexp := regexp.MustCompile(`\A[\pL_][\pL\p{Nd}_]*\z`)
>
> You can play with these regexps on play.golang.org.
>
> Is this simply an oversight that Unicode character classes like "Letter" and
> "Number, decimal digit" are not available for use in regexps, or should I be
> using them differently?
The strings you can use with \p are the ones listed in
unicode.Categories and unicode.Scripts. So use \pL as you do in the
second example.
Ian
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