The University of Iowa
The College of Liberal Arts and Sciences
Department of Computer Science
Programming Languages and Tools:
CS:3210:0001
Lecture/Lab #10
Programming with C++
Function overloading, overload resolution, member functions
Warm up
-
What will be the output of the following program?
int main() {
auto const n = 17;
n = -3;
std::cout << n;
}struct point {
int x;
int y;
};
void move_by( point& p, point const& offset ) {
p.x += offset.x;
p.y += offset.y;
}
int main() {
point const p = { 5, 5 };
move_by( p, point{ -1, 1 } );
std::cout << p.x << ", " << p.y << std::endl;
}
-
How about this one?
Function overloading
void print( int ); // prints an integer
void print( double ); // prints a floating-point number
void print( std::string ); // prints a string
int main()
{
print( 42 ); // calls print( int )
print( 9.65 ); // calls print( double )
print( "Barcelona" ); // calls print( std::string )
}
One of the characteristic features of C++ is function overloading: the ability to define more than one function with the same name in the same scope:
If two functions are defined with the same name, but with different argument types, the compiler will choose the most appropriate function to invoke for each call.
Function overloading (cont.)
- Overloaded functions must differ from each other by the types and/or the number of arguments
- The function that is the best match to the arguments supplied in the function call is called
- The process of selecting the best matching function is called overload resolution:
- The compiler performs name lookup to build a set of candidate functions
- The compiler examines function call arguments and candidate functions' parameters to reduce the candidate functions set to the set of viable functions
- For each pair of viable functions, the implicit conversions for each argument are ranked to determine which one is better
- If exactly one viable function is better than all others, overload resolution succeeds and this function is called. Otherwise, compilation fails.
Exercise 1
Define overloaded function `divide` that mimics the behavior of the built-in operator `/`
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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)
-
Click on the corresponding option in the "Lab10 exercises" poll in #general
Member functions
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A member function is a function that is defined as part of a class.
-
Member functions are sometimes referred to as methods.
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Member functions are accessed the same way as class' data members:
obj.mem_func()-
Member functions that do not modify the object's state should be marked as const.
-
Member function's definition can be provided outside of the class.
-
Member functions are in the class scope and have implicit access to other class members.
Member functions (cont.)
class point():
def __init__( self, x, y ):
self.x = x
self.y = y
def move_by( self, offset ):
self.x += offset.x
self.y += offset.y
def main():
p = point( 1, -1 )
p.move_by( point( -1, 1 ) )
main()
struct point {
point( int x, int y )
: x( x ), y( y ) {}
void move_by( point const& offset )
{
x += offset.x;
y += offset.y;
}
int x;
int y;
};
int main() {
point p( 1, -1 );
p.move_by( point( -1, 1 ) );
}Python
C++
Exercise 2
Implement member function `print` that takes a standard output stream and prints point's coordinates
-
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 "Lab10 exercises" poll in #general
Programming with C++, Spring 2020, Lecture #10
By Aleksey Gurtovoy
Programming with C++, Spring 2020, Lecture #10
Function overloading, overload resolution, member functions
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