#----------------------------------------------------------------------
# Building and stepping through lists
#
# Copyright (C) September 20, 2017 -- Dr. William T. Verts
#----------------------------------------------------------------------

#----------------------------------------------------------------------
# Step through a list, printing each element one per line
#----------------------------------------------------------------------

def Lister(): 
    L = [4, 5.6, "frog", -3, "toad"]
    I = 0
    while (I < len(L)):
        print L[I]
        I = I + 1
    return

#----------------------------------------------------------------------
# Three forms of the range function:
#
#     range(N) generates list [0,1,2,3, ..., N-1]
#     range(10) gives [0,1,2,3,4,5,6,7,8,9]
#
#     range(M,N) generates list [M,M+1,M+2,M+3, ..., N-1]
#     range(10,20) gives [10,11,12,13,14,15,16,17,18,19]
#
#     range(M,N,P) generates list [M,M+P,M+2P,M+3P, ..., N-1]
#     range(10,20,3) gives [10,13,16,19]
#----------------------------------------------------------------------
    
#----------------------------------------------------------------------
# Build a list of squares of numbers from 0 to 10.
#
# Method #1: Build a list containing [0,1,2,3,...,10], step through
# that list squaring each entry.  Does NOT work with tuples!
#----------------------------------------------------------------------

def BuildSquares():
    L = range(11)            # L = [0,1,2,3,4,5,6,7,8,9,10]
    I = 0        
    while (I < len(L)):        
        L[I] = L[I] * L[I] 
        I = I + 1      
    return L
    
#----------------------------------------------------------------------
# Build a list of squares of numbers from 0 to 10.
#
# Method #2: Start with an empty list L, step through the integers
# from 0 through 10, and add a list with the square of each integer
# to the end of L.
#----------------------------------------------------------------------

def BuildSquares2():
    L = []
    I = 0        
    while (I < 11):        
        L = L + [I*I]      # L is a list, so I*I has to be in a list 
        I = I + 1       
    return L
    
#----------------------------------------------------------------------
# Build a list of squares of numbers from 0 to 10.
#
# Method #3: Start with an empty list L, step through a range of
# numbers from 0 through 10, and add a list with the square of each
# integer to the end of L.
# The for-loop steps the control variable (I in this case) through
# the elements of a list, one value for each pass through the loop.
# The list to step through can be an explicit list (3a) or the
# result of a range (3b, more common).
#----------------------------------------------------------------------

def BuildSquares3a():
    L = []
    for I in [0,1,2,3,4,5,6,7,8,9,10]:
        L = L + [I*I]
    return L    

def BuildSquares3b():
    L = []
    for I in range(11):
        L = L + [I*I]
    return L    
    
#----------------------------------------------------------------------
# On Friday we will expand on 3b to do the whole task in a single
# Python statement, called a list comprehension.
#----------------------------------------------------------------------