In the following C++ functions:
void MyFunction(int age, House &purchased_house)
{
// ...
}
void MyFunction(const int age, House &purchased_house)
{
// ...
}
In both, age
is passed by value. I am wondering if the const
keyword is necessary: It seems redundant to me, but also helpful (as an extra indication the variable will not be changing).
Does anyone have any opinion as to which (if any) of the above are better?
Best Answer
First, it's just an implementation detail, and if you put const there, don't put it in the declaration set (header). Only put it in the implementation file:
Whether or not a parameter is const in a definition is purely an implementation detail, and should not be part of the interface.
I've not seen this sort of thing often, and i also don't do this. Having the parameter const would confuse me more often than help, because i would immediately pattern-match-fail it to "const int &age" :) The matter of course is entirely different from having const at another level:
In this case, the const will affect whether the function can change the caller's argument. Const in this meaning should be used as often as possible, because it can help ensuring program correctness and improve self-documenting the code.