The University of Iowa
The College of Liberal Arts and Sciences
Department of Computer Science
Programming Languages and Tools:
CS:3210:0001
Lecture/Lab #9
Programming with C++
Operator overloading, const, references
Warm up
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What's a user-defined type?
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What does a constructor do?
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Is this valid C++? If so, what does it do?
struct point { int x{0}, y{0}, z{0}; };
point p = { .z=10 };
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What's wrong with the following code?
struct point {
point( int x, int y, int z ) {}
int x;
int y;
int z;
};
point p = { 5, 17, -10 };
Operator overloading
- Ability for C++ operators to have user-defined meanings on user-defined types
- Most most built-in operators in C++ can be overloaded.
- Overloaded operators are just functions with predefined names.
- An overloaded operator is called an operator function.
- We can't define our own custom operators that don't already exist in the language.
- Overloaded operators keep their precedence.
Exercise 1
Define missing `point` operators to make the program compile and pass the tests
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Open the exercise template
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Write your code, press Run to test
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When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)
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Click on the corresponding option in the "Lab9 exercises" poll in #general
const
A keyword that tells the compiler that the object or variable is not modifiable
int main() {
int const i = 7;
i = 10; // error
++i; // error
point const p( 0, -1 );
p.x = -1; // error
}
References
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A reference is an alias to another object/variable
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When we define a reference, we bind the reference to its initializer
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A reference variable cannot be left uninitialized
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Once initialized, a reference remains bound to its initial object. There is no way to rebind a reference to refer to a different object.
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All operations on a bound reference are operations on the object to which the reference is bound.
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A reference type is an example of a compound type; a compound type can be used anywhere where a built-in type can be used.
Exercise 2
Implement `add_to` function that takes two points and adds the second point to the first one
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Open the exercise template
-
Write your code, press Run to test
-
When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)
-
Click on the corresponding option in the "Lab9 exercises" poll in #general
Const references
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const reference == a reference to a const object
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Primarily used to optimize away unnecessarily copying of objects
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May refer to an object that is not const
Programming with C++, Spring 2020, Lecture #9
By Aleksey Gurtovoy
Programming with C++, Spring 2020, Lecture #9
Operator overloading, const, references
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