> Which textbooks would that be? I think for example at Scott Meyers books (Effective C++, More effective C++...).
I also read this in the 4th edition (includes C++11) of the C++ programming language (Stroustrup): "How do we choose among the ways of passing arguments? My rules of thumb are: [1] Use pass-by-value for small objects. [2] Use pass-by-const-reference to pass large values that you don’t need to modify." is a string a large object??? >> The standard <string> library can implement copy on write but it is >> not mandatory and we should not rely on that behaviour. > > In C++11, rvalue string copies with move semantics are O(1). How are you sure you always get rvalues? Also the move semantics cannot be as quick as passing a reference. and I thought the move to C++11 is not forseen in a near future. >> Also the compiler may do some optimizations and remove some copies >> him-self but should we rely on a particular compiler to do our job >> when it is so "easy" to write efficient code? > > You should have rather written "efficient" in quote marks as long as > there is no evidence that the current code is less efficient under some > known compilers. I did not say that but you have the guarantee that with 'const string &' the code is at worst as efficient as today's code. > const string & as return type is madness. For one thing, it's > guaranteed _not_ to be an efficiency gain in C++11. For another, it > produces _serious_ destructor/lifetime issues. Of course I am not speaking of new strings created in the function! That would be stupid. But if you return a member of an object for example, it is stupid to return a copy of it (I do not know if this happens, however). Frédéric _______________________________________________ lilypond-devel mailing list lilypond-devel@gnu.org https://lists.gnu.org/mailman/listinfo/lilypond-devel
