Cairo's Assert statements can be used for 2 different use cases:

  1. Check if two variables are the same
  2. Set a variable's value if it's currently not set

Note that the usage of assert can feel unintuitive at times as asserts also set values rather than just checking the value of it.


func main():
    tempvar a = 1
    tempvar b

    # Check if `a` is set to `1`.
    assert a = 1

    # One might assume that this checks if `b` is set to `1`.
    # However given that `b` is not set yet, it'll be set to
    #   `1` via this `assert` usage.
    assert b = 1

    # Check if `b` is set to `2` which will fail.
    assert b = 2

    return ()