Re: zregexparse

[Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>]

On Apr 1,  9:43am, Bart Schaefer wrote:
}
} This is just one of the corners of the code that has not been paid
} any attention in a very long time (it's essentially unchanged since
} 2001 or so).

Also, I just looked a little more closely at the code to find out why
Sebastian's first example with '{print $match[1]}' seemed to output
something useful, and realized that zregexparse is built on top of
the globbing pattern matcher -- it builds a state machine for the
regular expression semantics that weren't yet part of extendedglob at
the time, and then steps through the state machine calling back for
each subexpression found; but otherwise it's globbing.

That's how/why $match[1] gets set (and reset) for each callback.

Oh -- Sebastian also remarked "just that shipping own regex engine is
extreamly cool, at least for me" -- Src/pattern.c is explicity (for
licensing reasons!) derived from Henry Spencer's regular expression
package, so zsh *is* "shipping own regex engine", it merely calls it
extendedglob instead.

The equivalent (though perhaps not easily a syntactic duplication) of
zregexparse probably could now be rewritten entirely with extendedglob.
E.g. here's a fragment of it:

    zrp() {
      setopt localoptions extendedglob
      local var1=$1 var2=$2 string=$3 pattern=$4 callback=$5
      local _zrp_cb='typeset -g $var1=$mend[1] $var2=$mend[1]'
      {
	functions[_zrp_cb]="$_zrp_cb;$callback;return 0"
	functions -M _zrp_cb
	: ${string//(#b)($~pattern)/$((_zrp_cb()))}
      } always {
	functions +M _zrp_cb
	unfunction _zrp_cb
      }
    }

torch% zrp p1 p2 abc 'bc|?' '{print "$p1, $p2, $mbegin[1], $mend[1], $match[1]"}' 
1, 1, 1, 1, a
3, 3, 2, 3, bc