Re: Match empty string at begin/end of symbol

[Teemu Likonen]

Joe Riel [2018-07-04 11:43:46-07] wrote:

> The regular expressions '\_<' and '\_>'
> seem to be broken in Emacs 25.1.1.  Consider
>
> (let ((str "3+ab"))
>   (and (string-match "\\<[a-zA-Z][a-zA-Z0-9]*" str)
>        (match-string 0 str)))
>  
> That returns "ab", as expected.  Change the "\\<" to "\\_<"
> and it no longer matches.  Why not?
>
> (let ((str "3+ab"))
>   (and (string-match "\\_<[a-zA-Z][a-zA-Z0-9]*" str)
>        (match-string 0 str)))

Because "+" is a symbol character too. See this:


    ELISP> (let ((str "3+ab"))
             (and (string-match "\\_<.+\\_>" str)
                  (match-string 0 str)))

    "3+ab"



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