64 bit integer arithmetic expression interpreter by Igor van den Hoven.

No restrictions on use.

Operator        Priority     Function
         ————————————————
         !               0            logical not
         ~               0            bitwise not
         *               1            integer multiply
         /               1            integer divide  
         %               1            integer modulo  
         d               1            integer random dice roll
         +               2            integer addition
         -               2            integer subtraction
         <<              3            bitwise shift
         >>              3            bitwise shift
         >               4            logical greater than
         >=              4            logical greater than or equal
         <               4            logical less than
         <=              4            logical less than or equal
         ==              5            logical equal (can use wildcards)
         !=              5            logical not equal (can use wildcards)
          &              6            bitwise and
          ^              7            bitwise xor
          |              8            bitwise or 
         &&              9            logical and
         ^^             10            logical xor
         ||             11            logical or 

         Parentheses work as expected, strings must be enclosed in quotes and
         are evaluated with strcmp.

         Example: mathexp("(1+2) * 3 << 4"); would return "144".