Re: Strange output in loop
On Nov 6, 2:23 pm, riva <ra.ravi....@gmail.com> wrote:
#include <iostream>
using namespace std;
int main(void)
{
int i=0;
while(char c = cin.get() != EOF) {
i++;
cout << i << c << endl;
}
}
I am a C programmer and I am learning C++ from Thinking in C++.
Are you a C programmer? The problems with the above code would
be problems in C as well.
The problems with the above code are:
1) i is incremented twice and the output is printed twice.
2) c is not printed.
The first problem with the above code is that EOF is out of band
information; cin.get() (like fgetc()) returns an int, not a
char, so that it can represent this information, as well as all
characters. So you need to declare c to be an int, and later
cast it to char once you've determined that it isn't EOF.
The second problem is that you're trying to do too much in one
statement, and getting confused about the precedences. It would
be far better to write the above:
int
main()
{
int i = 0 ;
int c = std::cin.get() ;
while ( c != EOF ) {
++ i ;
std::cout << i << static_cast< char >( c ) << std::endl ;
c = std::cin.get() ;
}
return EXIT_SUCCESS ;
}
By doing one thing at a time, you avoid obfuscation, and ensure
the correct ordering. (The correct ordering can also be ensured
by parentheses, but that doesn't do anything for the
obfuscation.)
A more typical C++ idiom, however, would be to use the status of
the istream to detect EOF:
int i = 0 ;
char c ;
while ( std::cin.get( c ) ) {
++ i ;
std::cout << i << c << std::endl ;
}
It's probably a matter of taste which one you use, but I think
the second is more idiomatic for C++ (where as long time C
programmers like myself still tend to use the first a lot).
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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