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?

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.

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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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

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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.

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.

Quote:

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Originally Posted by cpjust

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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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.

Quote:

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Originally Posted by brewbuck

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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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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Mats

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

Greetings