"Functional" Switchcase Example

switch_demo.py

from codetransformer.transformers.switchcase import switch


def foo(x):
    print("Start: x={}".format(x))

    with switch(x) as case:
        @case(1)
        def _1():
            # Read and write x.
            x = 'x was ' + str(x)
        @case(2)
        def _2():
            # Introduce a new "local".
            y = 'introduced y'
        @case(3)
        def _3():
            # See the mutations from cases 1 and 2.
            z = {'x': x, 'y': y}
            break_  # Break out of the case construct.
        @case(4)
        def _4():
            assert False, "Shouldn't be hit."

    # See the mutations introduced in the cases.
    print("End: x={!r}, y={!r}, z={!r}".format(x, y, z))


foo(1)
# Prints:
# -- Start: x=1
# -- End: x='x was 1', y='introduced y', z={'y': 'introduced y', 'x': 'x was 1'}

foo(2)
# Prints:
# -- Start: x=2
# -- End: x=2, y='introduced y', z={'y': 'introduced y', 'x': 2}