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Questionchar+char issues Pin
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Questionactivex dll problem [solved] Pin
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Questionpoint reference VS value Pin
sharion18-Apr-09 21:18
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AnswerRe: point reference VS value Pin
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GeneralRe: point reference VS value Pin
sharion19-Apr-09 1:35
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GeneralRe: point reference VS value Pin
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GeneralRe: point reference VS value Pin
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GeneralRe: point reference VS value Pin
sharion19-Apr-09 3:21
sharion19-Apr-09 3:21 
GeneralRe: point reference VS value Pin
Stuart Dootson19-Apr-09 3:52
professionalStuart Dootson19-Apr-09 3:52 
sharion wrote:
Based on experience previous, I take it for granted that whatever you have done to p have the same effect to str. That is passing by reference what I previously thought


What you are actually doing in your code is passing the pointer str by value. At the same time, you are passing by reference is what str points to.

C always passes parameters by value. So, when you want to pass a parameter by reference, you need to get a pointer to the value and pass the pointer by value to the function. So, this function takes x by value and returns a value calculated from x.

int Double(int x)
{
   return x + x;
}


while this function does the same, but passing x by pointer. To show that the actual value you pass to the function is not the one you're passing by pointer, I've changed the parameter to pX, meaning 'pointer to X'.

int Double(int *pX)
{
   return (*pX) + (*pX);
}


Now, let's move on to some string functions. Let's calculate the length of a C string:

int StringLength(char* s)
{
   int length = 0;
   while (*(s + length) != 0)
      ++length;
}


Now, what is s? It's a string, right? But in C, a string is just a pointer to the first character of the string! So, we're passing a pointer to the sequence of characters that make up the string. And we're passing that pointer by value. What we're passing by pointer is the characters that make up the string.

This page[^] and the ones it links to (especially the one about modifying function arguments[^] might help explain it better than I can - I've never been a good teacher Smile | :)

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

GeneralRe: point reference VS value Pin
Luc Pattyn19-Apr-09 4:05
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GeneralRe: point reference VS value Pin
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GeneralRe: point reference VS value Pin
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GeneralRe: point reference VS value Pin
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GeneralRe: point reference VS value Pin
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GeneralRe: point reference VS value Pin
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