regex - Parsing mathematical expressions in C# -

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as project, want write parser mathematical expressions in c#. know there libraries this, want create own learn topic.

as example, have expression

min(3,4) + 2 - abs(-4.6)

i create token string specifying regular expressions , going through expression user trying match 1 of regex. done front back:

    private static list<string> tokenize(string expression)     {         list<string> result = new list<string>();         list<string> tokens = new list<string>();          tokens.add("^\\(");// matches opening bracket         tokens.add("^([\\d.\\d]+)"); // matches floating point numbers         tokens.add("^[&|<=>!]+"); // matches operators , other special characters         tokens.add("^[\\w]+"); // matches words , integers         tokens.add("^[,]"); // matches ,         tokens.add("^[\\)]"); // matches closing bracket          while (0 != expression.length)         {             bool foundmatch = false;              foreach (string token in tokens)             {                 match match = regex.match(expression, token);                 if (false == match.success)                 {                     continue;                 }                  result.add(match.value);                 expression = regex.replace(expression, token, "");                 foundmatch = true;                  break;             }              if (false == foundmatch)             {                 break;             }         }          return result;     }

this works quite well. want user able enter strings expression. found question @ regex tokenize issue answer provide regex match text anywhere in expression. need match first occurrence @ front of expression can keep order of token. example see this:

5 + " smaller " + 10

should give me tokens 5 + " greater " + 10

if possible able enter escape characters user able use character " in strings, "this apostrophe \" " gives me token "this apostrophe " "

the answer wiktor stribiżew @ question looked good, couldn't modify matches @ beginning , 1 word. appreciated!

funny referencing question. adopted (yet again) my answer in there work here ;)

here's fiddle showing solution.

the regex 

(?!\+)(?:"((?:\\"|[^"])*)"?)

i changed code use capture groups able in simple manner not add surrounding quotes. loop removes + sign separating tokens.

regards


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