MTRN2500
Week 3 Lab02
WEDNESDAY 4PM - 6PM
THURSDAY 4PM - 6PM
Slides by Alvin Cherk (z5311001)
Info
These slides are based upon the lab document on Teams or on GitLab.com
Today
- Epsilon Testing (Assignment)
- More constructors i.e. copy and move constructors, copy and move assignment operators.
- Differences between methods, static methods, and friend functions.
- Operator overloading.
Epsilon Testing
Epsilon Testing
Floating point value representation in any computer language has some sort of error.
Sometimes, operations on floating point values may result in some sort of error, as such, when comparing the values of doubles, we cannot compare them directly.
Epsilon Testing
This is where epsilon testing comes in.
The idea is that we take the absolute value of the difference of the two numbers we are comparing.
If this difference is some really small number (near 0), then we say the values are equal.
epslion
difference of the two values we are comparing
Operator Overloading
Operator Overloading
Operator overloads allow you to decrease your code complexity and utilise well defined semantics
- C++ supports a rich set of operator overloads
- All operator overloads must have at least one operand of its type
- Advantages:
- Readability & reuse existing code semantics
- Save memory space, consistency, readability
- Flexible and easy to maintain
- No verbosity required for simple operations
- Disadvantages:
- Lack of context on operators
Only create an overload if your type has a single, obvious meaning to an operator
Operator Overloading
Operator Overloading
| Types | Operators | Member / Friend |
|---|---|---|
| I/O | <<, >> | Friend |
| Arithmetic | +, -, *, / | Friend |
| Relational, Equality | >, <, >=, <=, ==,!= | Friend |
| Assignment | = | member (non-const) |
| Compound assignment | +=, -=, *=, /= | member (non-const |
| Subscript | [] | member (const & non-const) |
| Increment/Decrement | ++, -- | member (non-const) |
| Arrow, Defrefernece | ->, * | member (const & non-const) |
Friends
Friends
A friend operator operates on two instances whereas a member operator operates on itself and brings in something else.
- Use friends when:
- The data should be available to everyone
- There is a piece of code very related to this particular class
Static vs Friends
When should one use these different function types?
- We should prefer methods by default since this provides the best security for member variables of an object.
- We should prefer static methods only if we can say yes to the following methods:
- Is this method closely related to the class it's declared in? And,
- Does it make sense to call this method when there's no object?
- We should prefer friend functions:
- For specific operator overloads.
- If our friend function wants to be friends with more than 1 class.
Rule of 5
Rule of 5
When writing a class that manages heap resources, we have to consider the "rule of 5"
- Destructor
- Copy constructor
- Copy assignment
- Move assignment
- Move constructor
*Apparently you didn't need to learn this, but its good to know & you are implementing it all in the assignment anyway
Code Demo
SharedPointer.cpp Continuation
Code Demo
Implement a shared pointer to an int in a class called SharedPointer. The specification for SharedPointer is given below:
or look at the pdf on teams
Code Demo
Complex.cpp
Code Demo
Create a Complex class that models a complex number and implement various member functions and operator overloads.
Code Demo
Robot.cpp
Code Demo
Feedback
MTRN2500 Week 3 Lab 2 22T3
By kuroson
