Regex For Me

I never fully understood existing regex syntax and rules, so I chose to implements mine!

It is possible to generate regex rules for string or programmatically.

Regex Syntax

Some syntax:

• a:z (Range) return TRUE if the char is between a and z included
• * (All) return TRUE for any char
• abc (Sequence) return TRUE if the sequence abc exist in the string at the iterator position
• R1|R2 (Or) return TRUE if one of the 2 rules is TRUE
• R1&R2 (And) return TRUE if both of the 2 rules are TRUE
• #R1 (Any) return TRUE always and iterate until the rule is TRUE
• =NR1 (Exact) return TRUE if the rule is TRUE exactly N times
• >NR1 (Minimum) return TRUE if the rule is TRUE at least N times
• <NR1 (Maximum) return TRUE if the rule is TRUE maximum N times
• (..) (Nested Rule) return TRUE if the rule inside the parenthesis is TRUE
• \ (Special chars) special chars such as | or & or \ or any other can be used in rules by adding \ before.

Example:

A simple regex to find markdown links is [(#!])]\((>1!\))\). To compile the rule:

 Regex * r = parse("[(#!])]\\((>1!\\)))");

If you want to be sure that is not an image just put (!\!) before the previous rule. Note that (!\!) is equal to (*&!\!).

A more complex regex to find markdown tables is \|(>1!\|)\|(#!\n)\n\|(\:|-)(>1-&!((\:|-)\|)\|(#!\n)\n the code is the following:

 const char *str = "| A | B |\n"
                   "|:-:|--:|\n";

 size_t n = strlen(str);
 Regex * r = parse("\\|(>1!\\|)\\|(#!\n)\n"
                   "\\|(\\:|-)(>1-&!((\\:|-)\\|))(\\:|-)\\|(#!\n)\n");
 if (!r) {
   fprintf(stderr, "Parse error!");
   return -1;
 }

 size_t i = 0;
 Bool res = eval(str, &i, n, r);
 printf("Res: %s, at %c (%lu)\n", (res ? "true":"false"), str[(i-1)], i);
 regex_free(r);

The result of such code is

Res: true, at
 (20)