pass-by-value

How to pass objects to functions in C++?

由 ≡放荡痞女 提交于 2019-11-25 21:38:54
问题 I am new to C++ programming, but I have experience in Java. I need guidance on how to pass objects to functions in C++. Do I need to pass pointers, references, or non-pointer and non-reference values? I remember in Java there are no such issues since we pass just the variable that holds reference to the objects. It would be great if you could also explain where to use each of those options. 回答1: Rules of thumb for C++11: Pass by value , except when you do not need ownership of the object and

What's the difference between passing by reference vs. passing by value?

由 两盒软妹~` 提交于 2019-11-25 21:34:26
问题 What is the difference between a parameter passed by reference a parameter passed by value? Could you give me some examples, please? 回答1: First and foremost, the "pass by value vs. pass by reference" distinction as defined in the CS theory is now obsolete because the technique originally defined as "pass by reference" has since fallen out of favor and is seldom used now. 1 Newer languages 2 tend to use a different (but similar) pair of techniques to achieve the same effects (see below) which

What is the use of “ref” for reference-type variables in C#?

由 旧街凉风 提交于 2019-11-25 20:45:38
I understand that if I pass a value-type ( int , struct , etc.) as a parameter (without the ref keyword), a copy of that variable is passed to the method, but if I use the ref keyword a reference to that variable is passed, not a new one. But with reference-types, like classes, even without the ref keyword, a reference is passed to the method, not a copy. So what is the use of the ref keyword with reference-types? Take for example: var x = new Foo(); What is the difference between the following? void Bar(Foo y) { y.Name = "2"; } and void Bar(ref Foo y) { y.Name = "2"; } You can change what foo

What exactly is copy-on-modify semantics in R, and where is the canonical source?

由 為{幸葍}努か 提交于 2019-11-25 16:52:33
Every once in a while I come across the notion that R has copy-on-modify semantics , for example in Hadley's devtools wiki . Most R objects have copy-on-modify semantics, so modifying a function argument does not change the original value I can trace this term back to the R-Help mailing list. For example, Peter Dalgaard wrote in July 2003 : R is a functional language, with lazy evaluation and weak dynamic typing (a variable can change type at will: a <- 1 ; a <- "a" is allowed). Semantically, everything is copy-on-modify although some optimization tricks are used in the implementation to avoid
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