c# - RegExp: X number of matches => X number of replacements? -

using regular expressions i'm trying match string, has substring consisting of unknown number of repeats (one or more) , replace repeating substring same number of replacement strings.

if regexp "(st)[a]+(ck)", want these kind of results:

"stack" => "stock" "staaack" => "stooock" //so 3 times "a" replaced 3 times "o" "staaaaack" => "stooooock" 

how do that?

either c# or as3 do.

for as3 can pass function replace method on string object matching elements arguments array. can build , return new string 'a' replaced 'o'

for example:

        // first way explicit loop         var s:string="staaaack";         trace("before", s);         var newstr:string = s.replace(/(st)(a+)(ck)/g, function():string{           var ret:string=arguments[1]; // here match 'st'           //arguments[2] match 'aaa..'           (var i:int=0, len:int=arguments[2].length; < len; i++)              ret += "o";           return ret + arguments[3]; // arguments[3] match 'ck'         });         trace("after", newstr); // output stoooock          // second way array , join         var s1:string="staaaack staaaaaaaaaaaaack stack paaaack"         trace("before", s1)         var after:string = s1.replace(/(st)(a+)(ck)/g, function():string{             return arguments[1]+(new array(arguments[2].length+1)).join("o")+arguments[3]         })         trace("after", after) 

here live example on wonderfl : http://wonderfl.net/c/bowe