#
# this program generates a random string expression
#
# also shows the use of if/elif/else statements.
#
# pre-lists, hence a bit "primitive", we'll see a nicer
# way to do this later in the term.
#
# version 2 
#    uses methods with parameter and return values
#
# written by e.bonakdarian   oct 2009
#

from random import randint



############################################################
def get_Operator(op):
    # function maps the operator (op) into the appropriate
    # string values and returns them to the caller
    #
    # + == 0
    # - == 1
    # * == 2
    # / == 3

    if op == 0:
        str_val = ' + '
    elif op == 1:
        str_val = ' - '
    elif op == 2:
        str_val = ' * '
    else:
        str_val = ' / '   

    return str_val



############################################################
def generate_Expr():
    # generate an expression using random numbers.
    # expression will have 4 operands and 3 operators
    #
    # using 3 operators in expressions from (-, +, *, /)
    # operands in range 1 - 15

    # generate first operand
    val1 = randint(1, 15)
    # generate first operator
    op1 = randint(0, 3)

    # generate second operand
    val2 = randint(1, 15)
    # generate second operator
    op2 = randint(0, 3)

    # generate third operand
    val3 = randint(1, 15)
    # generate third operator
    op3 = randint(0, 3)

    # generate last operand
    val4 = randint(1, 15)

    print val1, 
    op1_str = get_Operator(op1)
    print op1_str,

    print val2,
    op2_str = get_Operator(op2)
    print op2_str,

    print val3,
    op3_str = get_Operator(op3)
    print op3_str,

    print val4


############################################################
def main():
    print 'Program generates a random of string expressions'
    generate_Expr()
    generate_Expr()
    generate_Expr()
    raw_input('\n<enter> to exit.')


main()