// test: echo -e 'prog (1, {set (1, 2), push (arg (1)), show});\ncall (1, 10);\nlen' | calc.exe -n | grep -q '=> 0'
// test: echo -e 'prog (1, {mem (2), sto (1, arg (1) - rcl (1) / 2)})\ncall (1, 1)\ncall (1, 2)\ncall (1, 3)\nprog (1, {mem (2), sto (2, rcl (1)), sto (1, arg (1)), rcl (2)})\ncall (1, 10)' | calc.exe -n | grep -q '=> 2.25'
// test: echo -e 'set (1, 2, -5, 6, -8, 9, -2, 23, 4)\nord\nshow' | calc.exe | grep -q 'stack: -8 -5 -2 1 2 4 6 9 23'
// test: echo -e 'prog (1, {set (1, 2), push (arg (1)), show});\ncall (1, 10);\nlen' | calc.exe -n | grep -q '=> 0'
// test: echo -e 'prog (1, {mem (2), sto (1, arg (1) - rcl (1) / 2)})\ncall (1, 1)\ncall (1, 2)\ncall (1, 3)\nprog (1, {mem (2), sto (2, rcl (1)), sto (1, arg (1)), rcl (2)})\ncall (1, 10)' | calc.exe -n | grep -q '=> 2.25'
// test: echo -e 'set (1, 2, -5, 6, -8, 9, -2, 23, 4)\nord\nshow' | calc.exe | grep -q 'stack: -8 -5 -2 1 2 4 6 9 23'