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Feb 12th, 2007

C++ const help

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I'm not that used to C++ and hoping that someone can help me out with the const keyword. If I make a parameter to a function 'const' ,and then try to reference it, like:

c++ Syntax (Toggle Plain Text)
 int some_func(const char* param){
  char* ptr = param;
  ...
}
 int some_func(const char* param){
  char* ptr = param;
  ...
}

to do something with it, the compiler gives the "invalid conversion from const char* to char*" when I try to pass in a parameter. The question is, is there some way to reference the 'param' while keeping it constant? or how can I fix the error message? Thanks in advance

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blackjack

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Feb 12th, 2007

Re: C++ const help

Why not just use std::strings?

iamthwee

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Feb 12th, 2007

Re: C++ const help

you can do this: char* ptr = const_cast<char*>(param;), but that defeats the purpose of using const in the first place. Casting out the const should be avoided whenever possible.

Last edited by Ancient Dragon; Feb 12th, 2007 at 2:39 pm.

Ancient Dragon

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Feb 12th, 2007

Re: C++ const help

Either using :

c Syntax (Toggle Plain Text)
const char* ptr = param ;
// or
char* ptr = const_cast<char*> (param) ;
const char* ptr = param ;
// or
char* ptr = const_cast<char*> (param) ;

But it would be interesting to know what you are trying to achieve here.....

~s.o.s~

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Re: C++ const help

Basically, I need to step through any array using pointers instead of the array indices. I changed my char* ptr to const char* ptr and it does work. Thanks.

blackjack

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Feb 12th, 2007

Re: C++ const help

Click to Expand / Collapse Quote originally posted by blackjack ...

Basically, I need to step through any array using pointers instead of the array indices. I changed my char* ptr to const char* ptr and it does work. Thanks.

But why would having a second const char* copy do you any good? Neither pointer can you modify, so copying it would be sort of pointless (sorry, bad pun).

John A

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