Re: Universal Character Names

>universal-character-name:
> \u hex-quad
> \U hex-quad hex-quad
>
>hex-quad:
> hex-digit hex-digit hex-digit hex-digit
>
>Needless to say this makes the old regexp for identifiers:
>
>[a-zA-Z_]+[a-zA-Z0-9_]*
>
>obsolete. How would you modify it to handle UCN?


>[a-zA-Z_]+[a-zA-Z0-9_]*


Here's what I was able to come up with based on the description you gave:




([a-zA-Z_]|((\\u[a-zA-Z0-9]{4})|(\\U[a-zA-Z0-9]{8})))([a-zA-Z0-9_]|((\\u[a-zA-Z0-9]{4})|(\
\U[a-zA-Z0-9]{8})))*


Since RE's like this are nasty, to say the least, I prefer to write these beasts out as if
I were coding:


        (
                [a-zA-Z_]
                |
                (
                        (
                                \\u[a-zA-Z0-9]{4}
                        )
                        |
                        (
                                \\U[a-zA-Z0-9]{8}
                        )
                )
        )
        (
                [a-zA-Z0-9_]
                |
                (
                        (
                                \\u[a-zA-Z0-9]{4}
                        )
                        |
                        (
                                \\U[a-zA-Z0-9]{8}
                        )
                )
        )*


Your particular re parser may use a bang for a pipe. If you re parser doesn't deal with
the {n} postfix, you'll have to make these replacements:


                                \\u[a-zA-Z0-9]{4}


becomes:


                                    \\u[a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9]


and


                                \\U[a-zA-Z0-9]{8}


becomes:




\\U[a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9
]


Since my eyes are tired, I leave such replacement within the full re
itself as an exercise for the reader... (Indeed, I may have missed a
"p" or "q" somewhere in that beastie...)


--
Quinn Tyler Jackson


email: qjackson@wave.home.com
url: http://www.qtj.net/~quinn/
ftp: qtj.net

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