from while loop to for loop -strings

[xcindiix]

Hey there,

i want to count the number of words on each line from an inputted file.

from an input the program will look like :

   cout << endl << "Enter a sentence in a line: " << endl;
   string a_line;
   getline(cin, a_line);
  
   int count = 0;
   istringstream src2(a_line);
   string a_word;
   while (src2 >> a_word)
     ++count;
   cout << "There are " << count << " words." << endl;

how can you convert it to a for loop? so that every line is read in the file?

[vlad from moscow]

I have not understood why is there necessary to use the for loop?

It is much simpler to write

int count = 0;
while ( std::getline( std::cin, line ) )
{
   count += std::distance( std::istream_iterator<std::string>( std::istringstream( line ) ), 
                           std::istream_iterator<std::string>() );
}

std::cout << "There are " << count << " words." << std::endl;

[xcindiix]

But im reading from a file ?

[vlad from moscow]

Then change std::cout to some ifstream. For example

std::ifstream file_stream( "MyFile" );

while ( std::getline( file_stream, line ) )
{
// ... 

[3CXz8vqX]

For loops are generally used when you know the exact amount of numbers you are dealing with. Otherwise if you don't and in this case, you're recommended to use while loops, since you don't know how long it's going to take for the loop to end.

You 'could' use a for loop with some tweaking but it just makes for confusing syntax.

[xcindiix]

i was thinking the number of for loops determined by the no. of lines in the file ?

[vlad from moscow]

To count the number of lines in the file you have to read all the lines.:) So there is no any sense in such an operation even if the first line contains some number that is considered as the total number of lines. In any case it is better to use the while loop because it is possible that some errors will occur during reading lines.

[xcindiix]

Thank you :)