A scientific calculator super easy to extend
Just follow the pattern in symbol variable (calculator.c) and add the desire symbol, then create a new static function for that symbol (static functions are also inside caculator.c) and that's it.
PD: The function should return a double.
PD2: This program was tested with valgrind, it has no memory leaks nor errors
gcc -lm main.c calculator.c stack.c stackn.c str.c queue.c -o calc
./calc "exp".
./calc "(5+6)*2 + sin(pi)"