regex for nested mark-up/functions -

i creating program offer few functions can entered user. let's have function convert string upper-case function $upper(string) , function $lower(string). user can enter in text box while using placeholders insert content (e.g. %t title of song). using both placeholders , functions, user can enter complete naming pattern.

functions can nested , want execute inner-most function first. looking regex identify it. in english, looking a function (and value) not contain function.

during tests, use hyphens instead of brackets , no $-sign. lot easier read. functions during testing lower-sometext-.

this guess far:

(lower|upper)-(?!((lower|upper)-.*-))- 

i read follows:

• find word upper or lower,
• followed hyphen,
• followed not word upper or lower, hyphen, random number of random characters , hyphen
• followed hypen.

but won't accept lower-sometext-. trying different things more 2 hours can't figure out...

use different approach: instead of looking inner-most function first, start outermost function - , resolve value recursively.

so string upper(lower(sometext)) first "handle" upper. before apply toupper() call same function on value - in case lower(sometext). same thing again: apply tolower() result of execute function value - in case sometext. since not contain function, execute method return sometext , end recursion.

i have created function in c#

public string execute(string text) {     string pattern = @"(lower|upper)\((.*)\)";     match m = regex.match(text, pattern);     if (m.success)     {         switch (m.groups[1].value)         {             case "lower":                 return execute(m.groups[2].value).tolower();             case "upper":                 return execute(m.groups[2].value).toupper();             default:                 return null;         }     }     else         return text; } 

and can call function string:

string result = "upper(lower(sometext))"; 

again: important part inside switch: before call tolower() or toupper() call execute method value. result of function literal , never contain function. also, scales well.