Testing and debugging

Testing

The assert_eq procedure can be used to test for (approximate) equality of two quantities. This is often useful to make sure that (intermediate) results in longer calculations have a certain value, e.g. when restructuring the code. The general syntax is

assert_eq(q1, q2)
assert_eq(q1, q2, ε)

where the first version tests for exact equality while the second version tests for approximate equality \( |q_1-q_2| <= \epsilon \) with a specified accuracy of \( \epsilon \). Note that the input quantities are converted to the units of \( \epsilon \) before comparison. For example:

assert_eq(2 + 3, 5)
assert_eq(1 ft × 77 in², 4 gal)

assert_eq(alpha, 1 / 137, 1e-4)
assert_eq(3.3 ft, 1 m, 1 cm)

There is also a plain assert procedure that can test any boolean condition. For example:

assert(1 yard < 1 meter)
assert(str_contains("bar", "foobar"))

A runtime error is thrown if an assertion fails. Otherwise, nothing happens.

Debugging

You can use the builtin type procedure to see the type (or physical dimension) of a quantity:

>>> type(g0)

  Length / Time²

>>> type(2 < 3)

  Bool

>>> type(sqrt)

  forall A: Dim. Fn[(A²) -> A]