# Program to demonstrate the use of lists to pass changes to parameters
# back to the caller through the argument list
#
# Matt Bishop, MHI 289I, Winter 2018

# 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[0], "and outp =", outp[0]
    # change the value of the first element of outp
    outp[0] = inp[0] + 10
    # announce the values to see if the change worked
    print "test ends: inp =", inp[0], "and outp =", outp[0]

# 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[0], "and b =", b[0]
# now make the call
testparam(a, b)
# announce the values in the caller, after the call
print "program ends: a =", a[0], "and b =", b[0]