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Function arguments: Pointers vs. References

In these two function headers:

   void func1( int *pv )
   void func2( int &v )

- What are the major differences?
- What are the key benefits of using one instead of the other?
- Will 'v' in effect be a pointer?

Thanks
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InteractiveMind
Asked:
InteractiveMind
5 Solutions
 
zephyr_hex (Megan)DeveloperCommented:
A pointer is an object containing the address in memory of another object; a
reference is an alias for another object.
A pointer can be null; a reference cannot.
A pointer can be re-seated (i.e., pointed at a different object); a
reference cannot.
A reference must be initialized (i.e., its refer-ee specified) when it is
created; a pointer can be uninitialized.

this may help, too : http://www.cs.nott.ac.uk/~pni/Papers/Tutorials/C++/ref-vs-ptr.html
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AlexFMCommented:
Internally pointer and reference are implemented by the same way. On Assembly level function has pointer parameter.
However, there is significant difference in C++ compiler level. Reference allows to chain overloaded operators. For example, all overloaded << stream operators return ostream&. This allows to write:

cout << n << m << endl;

cout << n is handled by ostream operator << (int). This operator returms ostream&, which allows to apply the same ostream operator << (int) to the next parameter m etc. Learning overloaded operators, you can see that they return reference to class object, their last line is:
return *this;

This is main advantage of reference. You can see extensive using of references in different C++ libraries, like STL. For simple functions like func1 and func2 the only difference is syntax.
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AxterCommented:
Experts like Herb Sutter, recommend preferring to use reference over pointer, because a reference argument is less ambiguous.

A function that takes a pointer, could be receiving a pointer to a single argument, or an array of objects.
You don't have this abiguity with a reference argument.
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rstaveleyCommented:
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Harisha M GCommented:
- What are the major differences?
Pointer creates a local variable, that holds the address of the parameter sent.
Reference means an alias

- What are the key benefits of using one instead of the other?
Pointer is compatible with C and many other languages and helpful while writing DLLs.
Also pointer always takes (considering 32 bit machine) 32 bits of memory.
Reference avoids creating another variable, as it is just another name for the original parameter

- Will 'v' in effect be a pointer?
No. v is a reference.
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AxterCommented:
FYI:
>>Pointer is compatible with C

This is not that important when creating class methods, or pointers to class objects that C can't use anyway.
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Harisha M GCommented:
Where did I mention classes ?
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AxterCommented:
>>Where did I mention classes ?

My comment was not meant to contradict your statement, but to give additional information.
Since this is the C++ topic area, I think it's important to point out that compatibility to C should not be a factor if you already have headers that are incompatible to C.

This point may not be obvious to a beginner, or to someone unfamiliar with C.
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Harisha M GCommented:
Use extern C :)
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InteractiveMindAuthor Commented:
Thanks very much all; 50 points to all participants.
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