calc_test.py

"""
Doctests for calc.py

Parser::

    >>> parse('1.0')
    1.0
    >>> parse('alpha')
    'alpha'
    >>> parse('(+ 1 2.5)')
    ['+', 1, 2.5]
    >>> parse('(* 4 (+ 1 2.5))')
    ['*', 4, ['+', 1, 2.5]]

Evaluator::

    >>> evaluate(1.0)
    1.0
    >>> evaluate('+')
    <built-in function add>
    >>> evaluate(['*', 6, 7])
    42
    >>> evaluate(parse('(/ (* (- 100.4 32) 5) 9)'))
    38.0

High-level function `calc`::

    >>> calc('+')
    <built-in function add>
    >>> calc('(* 111 111)')
    12321

Global environment::

    >>> global_env['-']
    <built-in function sub>
    >>> calc('(define n 1729)')
    >>> global_env['n']
    1729

"""


from typing import Optional

from pytest import mark

from calc import parse, evaluate, calc, Expression, global_env

# tests for parse

@mark.parametrize( 'source, expected', [
    ('7', 7),
    ('x', 'x'),
    ('(sum 1 2 3)', ['sum', 1, 2, 3]),
    ('(+ (* 2 100) (* 1 10))', ['+', ['*', 2, 100], ['*', 1, 10]]),
])
def test_parse(source: str, expected: Expression) -> None:
    got = parse(source)
    assert got == expected

# Norvig's tests for the calculator subset of Scheme

@mark.parametrize( 'source, expected', [
    ("(+ 2 2)", 4),
    ("(+ (* 2 100) (* 1 10))", 210),
    ("(define x 3)", None),
    ("x", 3),
    ("(+ x x)", 6),
])
def test_evaluate(source: str, expected: Optional[Expression]) -> None:
    got = evaluate(parse(source))
    assert got == expected

# tests for each of the cases in evaluate

def test_evaluate_variable() -> None:
    global_env['x'] = 10
    source = 'x'
    expected = 10
    got = evaluate(parse(source))
    assert got == expected


def test_evaluate_literal() -> None:
    source = '3.3'
    expected = 3.3
    got = evaluate(parse(source))
    assert got == expected


def test_define() -> None:
    source = '(define answer (* 6 7))'
    got = evaluate(parse(source))
    assert got is None
    assert global_env['answer'] == 42


def test_invocation_builtin_cos() -> None:
    source = '(cos 0)'
    got = evaluate(parse(source))
    assert got == 1.0


def test_invocation_builtin_random() -> None:
    source = '(random)'
    got = evaluate(parse(source))
    assert 0 <= got < 1