Re: function call misinterpreted as a variable

[Zara]

sjbrown8@eng.usf.edu wrote:
> I have the piece of code below, and when i try compiling with the line
>
> g++ 753075304.cpp
>
> I get the following error message:
>
> 753075304.cpp: In function 'int main()':
> 753075304.cpp:29: error: 'plus' was not declared in this scope
(...)
> #include <iostream>
> using namespace std;
> #include <cmath>
> double quad(double, double, double);
> double plus(double, double, double);
> double neg(double, double, double);
>
> int main()
> {
>     double xpos;
>     double a;
>     double b;
>     double c;
>     double square;
>     double xneg;
>
>     cout << "This program will compute a quadratic equation\n";
>     cout << "Please enter a number: \n";
>     cin >> a;
>     cout << "Please enter another number: \n";
>     cin >> b;
>     cout << "Please enter a final number: \n";
>     cin >> c;
>
>     square = quad(a,b,c);
>     xneg = neg(a,b,square);
>     xpos = plus(a,b,square);
>
>     cout << "The positive function is: " << xpos << "\n";
>     cout << "The negative function is: " << xneg << "\n";
>
>     return 0;
> }
(...)

I tried to compile it with GCC 3.4.2, adn it also failed.
The problem lies in a existing template version of plus in std 
namespace. I think it is a GCC bug, because AFAIK the compiler *should* 
prefer non-template functions, but anyhiw, there is a workaround:

substitute your line
  using namespace std;
with these two lines
  using std::cin;
  usign std::cout;

In general, you should try to limit your using clauses to specific 
classes or functions, avoiding using complete namespaces.

Best regards