''' Purpose: try out functions
'''

# This is a program (a tester for the module harb)
# Recall that modules / libraries (interchangeable terms) contain function definitions
# Function definitions look like this
# def function_name( parameters ):
    # function statements
    # return statement (possibly)
# WE call functions in one of two ways:
# variable = function_name( arguments ) <- arguments are passed in as the values for parameters
# function_name(arguments) <- This just calls the function if the function maybe doesn't return anything (changes something /
# executes function and moves on)
# If the function returns a value, that return value is stored in the variable on line 12.
# This file contains FUNCTION CALLS (invocations) of functions from the module harb
# harb has the function definitions!
import harb                             # import access to module harb

n1, n2 =  3, 14                         # get some values for function exploration
n3, n4 = 15, 92
n5, n6 = -6, 53

# Function calls:
# module_name.function_name( arguments )
# add has parameters a and b
# n1 and n2 are the arguments for a and b
# a takes on the value n1
# b takes on the value n2
# IMPORTANT the return value is stored in the variable that the function call is assigned to!
# ^^^^^^^^^ Please remember this!
# t1 stores the return value of the function call harb.add( n1, n2 )
# So t1 would be 17  since 17 is the return value from the function
t1 = harb.add( n1, n2 )                 # invoke harb.add() with arguments n1 and n2
                                        # return value used to set t1

t2 = harb.add( n3, n4 )                 # invoke harb.add() with arguments n3 and n4
                                        # return value used to set t2

print( "add(", n1, ",", n2, "):", t1 )  # print first  add() result
print( "add(", n3, ",", n4, "):", t2 )  # print second add() result

print()

i1 = harb.negate( n5 )                  # invoke harb.negate() with argument n5
                                        # return value used to set i1

i2 = harb.negate( n6 )                  # invoke harb.negate() with argument n6
                                        # return value used to set i2

print( "inverse(", n5, "):", i1 )       # print first  inverse() result
print( "inverse(", n6, "):", i2 )       # print second inverse() result


# i3 = harb.negate() # This will not work! You didn't give it anything as an argument for x!
# print( i3 )

# NUMBER OF ARGUMENTS HAS TO BE THE SAME AS THE NUMBER OF PARAMETERS.
# Don't give too many arguments or too little!

s1 = 'happy'
s2 = 'today'
a3 = harb.add(s1, s2) # 'happytoday'
# Will this add function still work if you give it two strings instead of numbers?
# Yes! Because the operator + adds for numbers but does string concatenation for strings
# print( a3 )

a1 = [3,1,4]
a2 = [1,5,9,2,6]
a4 = harb.add(a1, a2)
# print( a4 )
# print( result ) # The result variable is a local variable only known within the scope of the function
# harb so inger doesn't know what result is.
# print( harb.add.result ) # Same thing ^
# Local variables are variables defined in the scope of the function.
# Likewise, you can't do like
# print(a)
# or print(b)
# inger.py doesn't know what a and b are!
# Will this add function still work for lists?
# Yes! Because the + operator combines two lists

# x1 = 3
# x2 = 'apple'
# a5 = harb.add( x1, x2 )
# print( a5 )

# This function will NOT work for a string and an integer because you can't use
# + for a string and integer

# An important thing to remember is that we don't define the type of the parameters being passed in
# We can pass in strings, lists, numbers for a and b and Python will just evaluate the result
# based on whether or not it can execute the statements with the arguments you gave it

# It's based on legal Python but parameters are just placeholders for arguments.
# You don't define the type of the arguments beforehand.
# In Python you would do like
# def function_name( a, b):
# In Java, types of parameters ARE defined (but you don't need java for this class that's 2110) :)
# public void function_name( int a, int b)