Branch :
1 + 20 21 1 + 20 / 3 7 to_lisp(quote 1 + 20 / 3) [operator_add, 1, [operator_div, 20, 3]] 1 + 20 / 3 * 4 25 to_lisp(quote 1 + 20 / 3 * 4) [operator_add, 1, [operator_mul, [operator_div, 20, 3], 4]] 1 + 20 / 3 * 4 - 5 20 to_lisp(quote 1 + 20 / 3 * 4 - 5) [operator_sub, [operator_add, 1, [operator_mul, [operator_div, 20, 3], 4]], 5] 20 / 3 * 4 - 5 19 to_lisp(quote 20 / 3 * 4 - 5) [operator_sub, [operator_mul, [operator_div, 20, 3], 4], 5] (1 + 20) 21 to_lisp(quote (1 + 20)) [operator_paren, [operator_add, 1, 20]] a = (1 + 20) 21