// test: echo -e '1 +\n1 -\n1 * 1\n1 /\n3%\n2^\nsqrt ()\ncos ()\nsin ()\natan ()\nlog ()\nexp ()\n1 + (' | calc.exe | grep -c error | xargs test 11 =
// test: echo -e '1 + 1\nans' | calc.exe -p 3 | grep -c 2 | xargs test 2 =
// test: echo -e 'sin (pi / 2)' | calc.exe -p 4 | grep -q 1
// test: echo -e 'e ^ 2' | calc.exe | grep -q '7\.38906'
// test: echo -e '\n\n\n' | calc.exe | grep -qv 'error'
// test: echo -e '\n\n\n' | calc.exe -n
// test: echo -e '1 +\n1 -\n1 * 1\n1 /\n3%\n2^\nsqrt ()\ncos ()\nsin ()\natan ()\nlog ()\nexp ()\n1 + (' | calc.exe | grep -c error | xargs test 11 =
// test: echo -e '1 + 1\nans' | calc.exe -p 3 | grep -c 2 | xargs test 2 =
// test: echo -e 'sin (pi / 2)' | calc.exe -p 4 | grep -q 1
// test: echo -e 'e ^ 2' | calc.exe | grep -q '7\.38906'
// test: echo -e '\n\n\n' | calc.exe | grep -qv 'error'
// test: echo -e '\n\n\n' | calc.exe -n