Really simple references/char question

This is a discussion on Really simple references/char question within the C++ Programming forums, part of the General Programming Boards category; Hi, little problem with references, char*s and passing. To simplify the problem: Code: #include <iostream.h> char& foo(char& c, const char& ...

  1. #1
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    Really simple references/char question

    Hi, little problem with references, char*s and passing.

    To simplify the problem:
    Code:
    #include <iostream.h>
    
    char& foo(char& c, const char& d) {
      cout << c << " " << d << endl; 
      c = d;
      return c;
    }
    
    main() {
      char* c = "This is a test";
      char* d = "This is also a test"
      
      foo(c,d);
    
      cout << c;
    }
    This doesn't compile. I could pass foo(*c,*d), but then foo() will only have access to the first character.

    Insight?

  2. #2
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    You could do it like this. Pass the addresses of the strings and the function can use the strings.

    Code:
    char *foo(char *c, char *d) {
      cout << c << " " << d << endl; 
      c = d;
      return c;
    }

  3. #3
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    I don't suppose there's a way of doing that by using references in the argument list?

  4. #4
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    To do this the "C++" way you should use std::string instead of char *.

    Something like this..
    Code:
    #include <iostream> //DO NOT USE .h headers
    #include <string>
    using namespace std;
    
    
    //Note void. No need to return since you are using a reference
    void foo(string &c, const string &d) 
    {
      cout << c << " " << d << endl;
      c = d;
    }
    
    int main()
    {
      string c = "This is a test";
      string d = "This is also a test";
      foo(c, d);
      cout << c << endl;
      return 0;
    }

  5. #5
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    I suppose I was trying to mix to many different styles there. Thanks for the help.

    (by the way, I was returning char& so I could say something like cout << foo(a,b);)

    Does it really matter if you include the .h?

  6. #6
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    .h is non standard

  7. #7
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    but then foo() will only have access to the first character.
    Well... not true!

    Arrays are stored sequentially, so if your function can get-to the first character, it can get to 'em all. If fact, passing a pointer is the most common way of doing this sort of thing. (And the most common way of getting a function to update multiple variables.)

    If you're a "newbie", this may not mean much yet, but pointers are also used to pass structures and objects into functions.

    To do this the "C++" way
    mousey,
    FYI - Many books and instructors teach the "C way" first. (aka C-style strings, null-terminated strings, or character arrays.) So, you can hold-off on using <string> if that's the way your class/book is structured.

    [EDIT] The Windows API uses C-style strings too. Don't 'ya just love it when they teach you the hard way first!
    Last edited by DougDbug; 10-16-2003 at 12:27 PM.

  8. #8
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    Originally posted by DougDbug
    If you're a "newbie", this may not mean much yet, but pointers are also used to pass structures and objects into functions.
    Lol, I guess you could say I'm a newbie C++ programmer, but I'm experienced in Pascal and Basic (to an extent), and I've programmed in C before, so I know the basics .
    Arrays are stored sequentially, so if your function can get-to the first character, it can get to 'em all. If fact, passing a pointer is the most common way of doing this sort of thing. (And the most common way of getting a function to update multiple variables.)
    So I could actually iterate through the string after passing it? I didn't actually think of this, as soon as reading the pointer only revealed the first character, I gave up .

    Thanks for the info.

  9. #9
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    If you use foo(*c, *d) as you mentioned and then take the address of your parameters in foo(), you will get the c-string as you would expect.

    Code:
    #include <iostream>
    
    void foo(char& c)
    {
      std::cout << &c << std::endl;
    }
    
    int main()
    {
      char* c = "hello world";
      foo(*c);
    }

  10. #10
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    Thanks, that's really useful

  11. #11
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    use * or [] when refering to C style strings. I can't think of an appropriate use for & when it comes to C style strings----though I suspect somebody may prove me wrong very shortly.

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