pass-by-value

I've always heard that a good practice to ensure best performance was to: pass fundamental types ( int , double ...) by value pass classes by const reference Nowadays, using C++11 and full optimizations under a compiler, is there an overhead when one passes a fundamental type by const reference? And furthermore, when T is int will the following function: template <typename T> inline void f(const T& x); be slower than: template <typename T> inline void f(const T x); If the compiler is really inlining the code (which is common for simple templates) there will be no difference. The problem

I know that in Matlab, there is a 'lazy' evaluation when a new variable is assigned to an existing one. Such as: array1 = ones(1,1e8); array2 = array1; The value of array1 won't be copied to array2 unless the element of array2 is modified. From this I supposed that all the variables in Matlab are actually value-type and are all passed by values (although lazy evaluation is used). This also implies that the variables are created on the call stack. Well, I am not judging the way it treats the variables, although I have never seen a second programming language doing this way. I mean, for possibly

I'm using a subroutine to make a few different hash maps. I'm currently passing the hashmap by reference, but this conflicts when doing it multiple times. Should I be passing the hash by value or passing the hash reference? use strict; use warnings; sub fromFile($){ local $/; local our %counts =(); my $string = <$_[0]>; open FILE, $string or die $!; my $contents = <FILE>; close FILE or die $!; my $pa = qr{ ( \pL {2} ) (?{ if(exists $counts{lc($^N)}){ $counts{lc($^N)} = $counts{lc($^N)} + 1; } else{ $counts{lc($^N)} = '1'; } }) (*FAIL) }x; $contents =~ $pa; return %counts; } sub main(){ my

Many people say that in Python arguments to functions are passed using a call-by-value model. As I understand it, it is not actually a call-by-value language, but a call-by-object or call-by-sharing model. What are the differences between a call-by-value model and a call-by-object model? What is an example in Python that shows how these models are different? Saying that it is not pass-by-value is not correct. Semantically, it is pass-by-value, and one can demonstrate the semantic equivalence between it and other pass-by-value languages. However, it belongs to a particular subcategory of pass

This question already has an answer here: Is Ruby pass by reference or by value? 12 answers I am basically a java developer. I am working in ruby for about an year. Unlike java, Ruby is a pure object oriented programming language. Here comes a doubt. Is it pass-by-value or pass-by-reference? Java works as pass-by-value: "When passing primitives, I see that the value is duplicated and passed to the method. But incase of Objects, the reference is duplicated and passed to the method. The reference contains the location of the object in the heap. During the method call, only the location of the

In .NET, strings are immutable and are reference type variables. This often comes as a surprise to newer .NET developers who may mistake them for value type objects due to their behavior. However, other than the practice of using StringBuilder for long concatenation esp. in loops, is there any reason in practice that one needs to know this distinction? What real-world scenarios are helped or avoided by understanding the value-reference distinction with regard to .NET strings vs. just pretending/misunderstanding them to be value types? The design of string s was deliberately such that you