#                                                        conditionals.py

# You need to understand boolean expressions to understand conditionals.
# If you are not familiar with them, consult [Downey].

# absolute taking one argument returns the absolute value of the given
# number.  To compute the absolute value, it uses a conditional
# expression, i.e., if...else...  Both syntax and semantics of a
# conditional expression is intuitive.
#
def absolute(x):
    if x < 0:
        return -x
    else:
        return x

absolute(-34)             # silent
print absolute(-34.4)     # not silent

# A conditional expression can be of the cascaded if...elif... ...else...
# form if you need to have multiple cases to handle, again intuitive.
# Note, that if you define functions with the same name multiple times,
# the last one overwrites all the previous ones even if their signatures
# are different (unlike how it is in Java.  Java supports function name
# overloading, but not in Python.).
#
def absolute(x):
    if x < 0:
        return -x
    elif x > 0:
        return x
    else:
        return 0

print "absolute(-34) = ", absolute(-34)
print "absolute(34) = ", absolute(34)
print "absolute(0) = ", absolute(0)



# Exercise 1:
#
# Write a boolean function that determines if a given speed value is within
# the legal freeway speed on I-10 outside of the city limits.  Once you define
# the function, write a piece of code that calls (aka uses/invokes/applies) the 
# defined function and prints the computed result (true or false).



# Exercise 2:
#
# Given a score out of 100, return a letter grade for the score.  Let's assign
# the letter grade using the grading scale given by the following table:
#
#   above 89: A
#   above 79 and below 90: B
#   above 69 and below 80: C
#   above 59 and below 70: D
#   below 60: F
#
# and call the function at least five times, each time producing a different
# letter grade.
#
# It is okay to produce the final grade as a string value, e.g., "A" for an A.


# Exercise 3:
#
# See Section 5.14 of [Downey] if you want to see more exercise problems.


# A side note: In Python a function name cannot be overloaded.  That is, you
# cannot define a function with different parameter lists to mean different
# functions.  For example, if you redefine absolute with two parameters, the
# one with one parameter that you defined earlier is lost.
#
# So, you can call absolute with one argument okay here
#
print absolute(-23)

def absolute(x, y):
    return x + y

# But, you cannot call absolute with one parameter here any more, thus I
# commented it out here.
#
# print absolute(-23)
#
# Of course, this one below would certainly be okay.
#
print absolute(2, 3)