are "const int&" parameters useful?

This is a discussion on are "const int&" parameters useful? within the C++ Programming forums, part of the General Programming Boards category; hi guys i was wondering if i should rigorously stick to passing by reference. i was wondering if someone knew ...

  1. #1
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    are "const int&" parameters useful?

    hi guys

    i was wondering if i should rigorously stick to passing by reference.

    i was wondering if someone knew what kind of effect passing a const int by reference would have? ( what about doubles or shorts? )

    does it also make my programs perform faster or would it make them slower?
    Last edited by symbiote; 03-14-2009 at 01:13 PM.

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    It depends, are you passing just one integer, or double, or are you passing 500,000 integers, or doubles?

    When you pass by value a copy of what your are passing to the function is made in memory. If what you are passing is large it would take a while to copy all of that information.

    But for just a single, or few, integers or doubles, that copying won't effect performance.

    Passing by const reference ensures that the functions being called do not change the contents of what is being passed.

    Hope I said all of the right.

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    thanks for the response Phyxashun,
    i see.

    what i'm wondering now is, whether there is a cost in passing an int by reference.
    - and if it exist, wheter it would be more or less than the copy of the int

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    Quote Originally Posted by symbiote
    what i'm wondering now is, whether there is a cost in passing an int by reference.
    - and if it exist, wheter it would be more or less than the copy of the int
    It is likely to be the same cost as passing a pointer, since references are typically implemented as const pointers. Where the size of a pointer is equal to the size of an int, the cost would then be in pointer dereference. Either way, it is a marginal cost.
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    I think the benefit of passing by reference only comes when the object being passed is larger than a pointer. So passing primitive data types like int, char... by reference probably wouldn't make a difference, but passong structs & classes would make a noticable difference.
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    Quote Originally Posted by cpjust View Post
    I think the benefit of passing by reference only comes when the object being passed is larger than a pointer. So passing primitive data types like int, char... by reference probably wouldn't make a difference, but passong structs & classes would make a noticable difference.
    There are other effects, though. If the object being passed is an extremely small object (say, the size of an integer), the pass-by-value will cause a copy constructor to be invoked, whereas passing by reference will not. So that's a measurable change in behavior.
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    Quote Originally Posted by brewbuck View Post
    There are other effects, though. If the object being passed is an extremely small object (say, the size of an integer), the pass-by-value will cause a copy constructor to be invoked, whereas passing by reference will not. So that's a measurable change in behavior.
    But of course, for standard C++ basic types such as int, the built-in copy constructor is a simple move instruction [or something to that effect], which is about as little as could possibly be.

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    thank you for your insight everyone!
    i think i don't think i'll be passing primitive types by reference for reasons.

    Greetings

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