// test: echo -e 'si\t\t (pi / 2)' | calc.exe | grep -q '=> 1'
// test: echo -e '\t\t' | calc.exe | grep -q 'print'
// test: echo -e '1 + 1;\nans + 1' | calc.exe | grep -qv 2
+// test: echo -e 'mem\nsto (4, pi)\ndisp' | calc.exe | grep -q "storage: 0 0 0 3.14159 0 0 0 0 0 0"
+// test: echo -e 'mem (0)\nsto (2, pi)\ndisp' | calc.exe | grep -q "storage: 0 3.14159 0 0 0 0 0 0 0 0"
// test: echo -e 'mem\nmem (3)\nsto (4, pi)' | calc.exe | grep -q "error out of bound"
// test: echo -e 'mem (-1)' | calc.exe | grep -q "error"
// test: echo -e 'sto (2, 3)\nmem (2)\ndisp' | calc.exe | grep -q 'storage: 0 3$'