Unit5-06: Pass By Reference (ICS3U Only - Optional)

Learning Outcome

At the end of this lesson, you will be able to:

What is a default value in programming?
Where is the default value located in the list of parameters in a function definition?
What is the default value set to in Python?
What is the default value set to in C++?
Write the code for a function in Python called print_name that will display the full name of a person in CAPS). The person may or may not give a middle initial.
The function call look as follows:
print_name (u_fname, u_lname, u_minitial)
There are the 2 possibilities of what could be displayed:
SOPHIE A. STUDENT
SOPHIE STUDENT
Write the code for a function in C++ called DisplayInfo that will display the name of a person in CAPS. The person may or may not give their age.
The function call look as follows:
DisplayInfo (uName, uAge);
There are the 2 possibilities of what could be displayed:
LEROY JAMES
LEROY JAMES, 24

from the online book Computer Based Problem Solving by Patrick Coxall, read:
- By Value or By Reference
Pass By Value:
- passes a copy of the argument. Therefore, the original can never be modified.
Pass By Reference:
- passes the address of the argument. Therefore, the original CAN be modified.
Note: the Python language does NEITHER pass by value nor pass by reference. Instead it does "Pass by Object Reference".
- In order to achieve the behaviour of pass by reference, we pass a list so that we can then modify its contents.

use the syntax &someVariable in the function definition to reference its address

Create a program called “Rounding Program” that accepts numbers with decimals and rounds them according to a given number of decimal places.
Name the function: “round_decimal()” in Python and “RoundDecimal()” in C++.
The function will accept 2 parameters: the decimal number passed by reference and the number of decimal places to round
The function will not return anything
You CANNOT use any built-in rounding function.
Look at these steps to round the decimal:
- Multiply the decimal number by 10 to the power of the number of decimal places to round
- Add 0.5
- Convert the decimal to an integer. Hint: Try casting.
- Move the decimal point back to its original position by doing the opposite in step a.
For Python you cannot pass a primitive type (i.e. a float) by reference so you will have ot pass the variable in a list.
- Number_var = []
- Number_var.append(number)

in groups of 2, do the following on the board for today's daily assignment:
- Top-Down Design
- Flow Chart
- Pseudocode
- Test Cases

complete the Daily Assignment section in Hãpara Workspace for this day
- if Hãpara is not working, make a copy of this document
- move it to your IMH-ICS folder for this course

recreate the same program in C++
- NOTE: you will most likely get the following error while doing style checking about pointers. That topic is well beyond this course. Just include it in your style check for now:

vocstartsoft:~/environment/temp $ cpplint main.cpp

main.cpp:11: Is this a non-const reference? If so, make const or use a pointer: float &number [runtime/references] [2]

Done processing main.cpp

Total errors found: 2

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