# Program to demonstrate the use of lists to pass changes to parameters
# back to the caller as return values
#
# Matt Bishop, MHI 289I, Fall 2021

# this routine tries changes outp
# parameters: inp, a list of one integer
#             outp, a list of one integer
def testparam(inp, outp):
    # announce the values on entry to the function
    print("test begins: inp =", inp, "and outp =", outp)
    # change the value of the first element of outp
    outp = inp + 10
    # announce the values to see if the change worked
    print("test ends: inp =", inp, "and outp =", outp)
    # return them
    return inp, outp

# call a function that changes parameter values
# and see if the change is reflected in the caller
# calls: testparam

# set the values to be used; note these are *lists*
a = 1
b = 2
# announce the values in the caller, before the call
print("program begins: a =", a, "and b =", b)
# now make the call
a, b = testparam(a, b)
# announce the values in the caller, after the call
print("program ends: a =", a, "and b =", b)