#------------------------------------------------------------
# Construction of Lists
# Copyright (C) February 8, 2017 -- Dr. William T. Verts
#------------------------------------------------------------



#------------------------------------------------------------
# Construction of a list L by running through a while-loop.
# Note that the list starts off empty, then each pass through
# the loop one new item [I] is added to the end of the list.
#------------------------------------------------------------

def Main1():
    L = []
    I = 0
    while (I < 10):
        L = L + [I]
        I = I + 1
    print L
    return
    
#------------------------------------------------------------
# This is the same as above, but uses a for-loop to replace
# the while-loop.  The for-loop initializes I to the first
# value from the range (which is 0), and runs the body of the
# loop for each successive member of that range.  Note that
# both Main1 and Main2 end up with L set to the list:
# [0,1,2,3,4,5,6,7,8,9], which could have been done much more
# easily by simply setting L = range(10).
#------------------------------------------------------------

def Main2():
    L = []
    for I in range(10):
        L = L + [I]
    print L
    return

#------------------------------------------------------------
# In this version, L is set to a list that CANNOT be
# generated by a simple range function.  For each value of
# I, half that value (as a float) is appended to the list.
# The result is [0.0, 0.5, 1.0, 1.5, ... , 4.0, 4.5]
#------------------------------------------------------------

def Main3():
    L = []
    for I in range(10):
        L = L + [I * 0.5]
    print L
    return
    
#------------------------------------------------------------
# The range function can only return lists of integers.
# However, a list comprehension can generate many different
# types of lists.  In this example, the list constructor [],
# the for-loop, and the computed expression are all folded 
# into the list comprehension.  This generates the same list
# as in Main3: [0.0, 0.5, 1.0, ..., 4.5]
#------------------------------------------------------------

def Main4():
    L = [I * 0.5 for I in range(10)]
    print L
    return

#------------------------------------------------------------
# Here is a case where there is an if-statement inside the
# fop-loop.  The expression I % 2 gives the remainder of
# dividing I by 2, and that is tested for equality with 1,
# so therefore the expression (I % 2 == 1) is asking if I is
# and odd number.  For each value of I taken from the range
# 0 to 9, only those values that are odd have half their
# value appended to the list.  That is, the list ends up
# as: [0.5, 1.5, 2.5, 3.5, 4.5]  (or half of the odd integers
# 1, 3, 5, 7, and 9).
#------------------------------------------------------------
        
def Main5():
    L = []
    for I in range(10):
        if (I % 2 == 1):
            L = L + [I * 0.5]
    print L
    return

#------------------------------------------------------------
# This returns the same value as Main5, but embeds both the
# for-loop and the if-statement into the list comprehension.
#------------------------------------------------------------
 
def Main6():
    L = [I * 0.5 for I in range(10) if (I % 2 == 1)]
    print L
    return
        
#------------------------------------------------------------
# Try these expressions in the interactive area on your own:
#------------------------------------------------------------
   
[0 for I in range(10)]
[I for I in range(10)]    # Is this dumb, or what?
[I*I for I in range(10)]
[sqrt(I) for I in range(10)]
[sqrt(I) for I in range(10) if I % 2 == 0]   
[I for I in "FROG"]
["*" + I + "*" for I in "FROG"]
   
#------------------------------------------------------------
# Simple Image Processing: Brighten Every Pixel in an Image.
# Every line except the def and the return contain functions
# that are SPECIFIC to JES, and are not part of standard
# Python.  This is where we will pick up next class.
#------------------------------------------------------------
   
def Main7():
    Filename = pickAFile()
    Canvas = makePicture(Filename)
    show(Canvas)
    
    for PX in getPixels(Canvas):
        setRed(PX, getRed(PX) + 20)
        setGreen(PX, getGreen(PX) + 20)
        setBlue(PX, getBlue(PX) + 20)
        repaint(Canvas)
        
    return