// test: echo -e 'prog (1, {set (1, 2), push (arg (1)), show})\ncall (1, 10)\nprog (1, {mem (1), sto (1, cos (arg (1)))})\ncall (1, pi / 2)\ndel (1)' | calc.exe -n | grep -q 'stack: 1 2 10'
// test: echo -e 'prog (1, {set (1, 2), push (arg (1)), show});\ncall (1, 10);\nshow\ndel (1)' | calc.exe -n | grep -q 'stack:$'
// test: echo -e 'prog (1, {set (1, 2), push (arg (1)), show});\ncall (1, 10);\nlen' | calc.exe -n | grep -q '=> 0'
// test: echo -e 'prog (1, {set (1, 2), push (arg (1)), show})\ncall (1, 10)\nprog (1, {mem (1), sto (1, cos (arg (1)))})\ncall (1, pi / 2)\ndel (1)' | calc.exe -n | grep -q 'stack: 1 2 10'
// test: echo -e 'prog (1, {set (1, 2), push (arg (1)), show});\ncall (1, 10);\nshow\ndel (1)' | calc.exe -n | grep -q 'stack:$'
// test: echo -e 'prog (1, {set (1, 2), push (arg (1)), show});\ncall (1, 10);\nlen' | calc.exe -n | grep -q '=> 0'