Question

There was some code like this:

// Convenience to make things more legible in the following code const float & x = some.buried.variable.elsewhere;  // Go on to use x in calculations... 

I have been told that the ‘const float &’ is ‘bad’ and should just be a plain float or const float.

I, however, could not think of a compelling reason other than ‘you don’t have to type ‘&”.

In fact, it seems to me that in some cases the original could be better, since compiler might not allocate extra stack space to the variable.

In other words, originally I could validly say:

assert(&x == &some.buried.variable.elsewhere) 

Whereas in the second case I cannot.

Also, the original seems to communicate intent better, in my view, since the whole point of a reference is to make an alias to another value.

Can anyone give me examples of where the ‘const float &’ version is worse than a plain ‘float’ or ‘const float’ in some tangible way?

Answer 1

I can’t think of a reason why const float & would be better than const float.

References make sense if you’re either worried about copies being made (which is irrelevant with a primitive type like float) or you want to be able to update a value across all instances that share the reference (which is irrelevant with const members).

On top of that, references in members are a huge pain in the neck* when it comes to initialization, and so they’d have to offer a significant advantage of the alternatives in order to be useful, and it’s clearly not the case with const float.

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* The FQA on references is always amusing and thought provoking