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Functions: Miles-Per-Gallon Examples
1. Initial version
% cat mileage1.cpp
// miles per gallon function
# include <iostream>
using namespace std;
double mileage( double begin, double end, double gals) // header
{
double mpg;
mpg = (end - begin) / gals;
return mpg;
}
int main()
{
double start, finish, gallons, mpg;
start = 33050.0;
finish = 33355.0;
gallons = 13.4;
mpg = mileage( start, finish, gallons ); // call
cout << "For distance = " << (finish - start) <<
" miles and "
<< gallons << " gallons
" << "\nthe mileage is "
<< mpg << " mpg\n";
cout << "End of main" << endl;
return 0;
}
% g++ mileage1.cpp
% a.out
For distance = 305 miles and 13.4 gallons
the mileage is 22.7612 mpg
End of main
2. Using a function declaration so main() can be the first function
in the source code file
% cat mileage2.cpp
// miles per gallon function
// use a function declaration
# include <iostream>
using namespace std;
double mileage( double begin, double end, double gals); // declaration
int main()
{
double start, finish, gallons, mpg;
start = 33050.0;
finish = 33355.0;
gallons = 13.4;
mpg = mileage( start, finish, gallons ); // call
cout << "For distance = " << (finish - start) <<
" miles and "
<< gallons << " gallons
" << "\nthe mileage is "
<< mpg << " mpg\n";
cout << "End of main" << endl;
return 0;
}
double mileage( double begin, double end, double gals) // header
{
double mpg;
mpg = (end - begin) / gals;
return mpg;
}
% g++ mileage2.cpp
% a.out
For distance = 305 miles and 13.4 gallons
the mileage is 22.7612 mpg
End of main
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