argc和argv遇到问题

Question

Trying to add command line arguments to my programs. So I was experimenting and cannot figure out this intellisense warning for the life of me. It keeps on saying it is expecting a ')', but I have no idea why.

Here is the code it does not like:

    // Calculate average
    average = sum / ( argc – 1 );   

Then it underlines the subtraction operator. Below is the full program.

#include <iostream>

int main( int argc, char *argv[] )
{
    float average;
    int sum = 0;

    // Valid number of arguments?
    if ( argc > 1 ) 
    {
       // Loop through arguments ignoring the first which is
       // the name and path of this program
       for ( int i = 1; i < argc; i++ ) 
       {
           // Convert cString to int 
           sum += atoi( argv[i] );    
       }

       // Calculate average
       average = sum / ( argc – 1 );       
       std::cout << "\nSum: " << sum << '\n'
              << "Average: " << average << std::endl;
   }
   else
   {
   // If invalid number of arguments, display error message
       // and usage syntax
       std::cout << "Error: No arguments\n" 
         << "Syntax: command_line [space delimted numbers]" 
         << std::endl;
   }

return 0;

}

Answer 1

The character you think is a minus sign is something else, so it is not parsed as a subtraction operator.

Your version:

average = sum / ( argc – 1 ); 

Correct version (cut and paste into your code):

average = sum / ( argc - 1 ); 

Note that calculating an average using integers might not be the best way to do it. You have integer arithmetic on the RHS, which you then assign to float on the LHS. You should perform the division using floating point types. Example:

#include <iostream>

int main()
{
  std::cout << float((3)/5) << "\n"; // int division to FP: prints 0!
  std::cout << float(3)/5 << "\n";   // FP division: prints 0.6
}

Answer 2

I tried to compile your code on my machine with g++ 4.6.3 and got the follow error:

pedro@RovesTwo:~$ g++ teste.cpp -o  teste
teste.cpp:20:8: erro: stray ‘\342’ in program
teste.cpp:20:8: erro: stray ‘\200’ in program
teste.cpp:20:8: erro: stray ‘\223’ in program
teste.cpp: Na função ‘int main(int, char**)’:
teste.cpp:16:33: erro: ‘atoi’ was not declared in this scope
teste.cpp:20:35: erro: expected ‘)’ before numeric constant

Looks like there is some strange char in that line. Remove and re-write the line fixed the error.