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Making this const

Started by c0nfUzEd Dec 28, 2001 at 3:55 AM 4 replies 350+ views

Original Post

Dec 28, 2001 at 3:55 AM

  
class vector {
public:
   double x, y, z;
   double length ();
};

.
.
.

void dostuff (const vector f) {
   double l = f.length ();
}

I have some code like this, which the compiler refuses to compile, because f is supposed to be const. How do I tell the compiler that the "this" argument to vector::length () is a const?

_Hal_

Dec 28, 2001 at 4:28 AM

c0nfUzEd

Do you need that f to be const? Why?

_________________________
Hal - Atena Developer
www.grupoatena.hpg.com.br

Edited by - _Hal_ on December 28, 2001 5:33:35 AM

c0nfUzEd

Dec 28, 2001 at 4:56 AM

It''s not absolutely necessary, but I dont change f in the function so it''s nice to be able to see that straight away.

Also I have inline functions that pass by reference, and I like to make them const if I can to help the compiler do its optimisations.

DrPizza

Dec 28, 2001 at 6:16 AM

Change it to read

  double length () const;

c0nfUzEd

Dec 28, 2001 at 6:22 AM

Ah, so thats where the const goes.

Cool, thanks

Stoffel

Dec 28, 2001 at 12:42 PM

FYI, your doStuff function is creating a copy of your vector. I would suggest passing-in the vector by reference:
void dostuff (const vector &f)

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