Steve Graegert wrote:
If a programmer has chosen to pass a reference rather than a value, even if no reference is actually required, intentions to improve run-time performance come into mind. It is much more intuitive to pass primitives by value and use references only where appropriate, since performance gains due to the use of the const qualifier are very small and negligible in most cases.
I am somewhat confused. As I see it, the usage of a const ref for passing a parameter by reference is to improve runtime performance, yes, but it is not through the "const" part of it. It is through the reference part of it, which avoids a copy of the parameter being constructed which can be costly with large classes or structs. The const part of it is only there to prevent the function from modifying the source data, whether intentionally or accidentally. There may be a side-effect of optimization, but at least to my understanding the intent of const here is making the source read-only. Is this understanding wrong?
I agree of course that in case of tiny tidbits of parameters like a few int-s, double-s or even std::string-s, there is not much meaning in using const ref-s, and it is more intuitive to pass these by value. It is only practically useful to pass big classes / struct-s by reference.
Shriramana Sharma. - To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
