// test: echo -e 'si\t\t (pi / 2)' | calc.exe | grep -q '=> 1'
// test: echo -e '1 + 1;\nans + 1' | calc.exe | grep -qv 2
// test: echo -e 'mem (3)\nsto (4, pi)' | calc.exe | grep -q "invalid index"
+// test: echo -e 'sto (2, 3)\nmem (2)\ndisp' | calc.exe | grep -q 'storage: 0 3$'
// test: echo -e 'disp' | calc.exe | grep -q "storage: 0 0 0 0 0 0 0 0 0 0"
// test: echo -e 'sto (3, 10)\ndisp' | calc.exe | grep -q "storage: 0 0 10 0 0 0 0 0 0 0"
// test: echo -e 'rcl (3)\ndisp' | calc.exe | grep -q "storage: 0 0 0 0 0 0 0 0 0 0"