pass-by-value

Pass by reference or pass by value? [closed]

由 和自甴很熟 提交于 2019-11-26 03:54:52
问题 When learning a new programming language, one of the possible roadblocks you might encounter is the question whether the language is, by default, pass-by-value or pass-by-reference . So here is my question to all of you, in your favorite language, how is it actually done? And what are the possible pitfalls ? Your favorite language can, of course, be anything you have ever played with: popular, obscure, esoteric, new, old... 回答1: Here is my own contribution for the Java programming language.

Are arrays in PHP passed by value or by reference?

由 痞子三分冷 提交于 2019-11-26 03:27:44
When an array is passed as an argument to a method or function is it passed by reference? What about doing this: $a = array(1,2,3); $b = $a; Is $b a reference to $a ? For the second part of your question, see the array page of the manual , which states (quoting) : Array assignment always involves value copying. Use the reference operator to copy an array by reference. And the given example : <?php $arr1 = array(2, 3); $arr2 = $arr1; $arr2[] = 4; // $arr2 is changed, // $arr1 is still array(2, 3) $arr3 = &$arr1; $arr3[] = 4; // now $arr1 and $arr3 are the same ?> For the first part, the best

Does Javascript pass by reference?

由 旧街凉风 提交于 2019-11-26 03:13:01
问题 Does Javascript pass by references or pass by values? Here is an example from Javascript: The Good Parts . I am very confused about my parameter for the rectangle function. It is actually undefined , and redefined inside the function. There are no original reference. If I remove it from the function parameter, the inside area function is not able to access it. Is it a closure? But no function is returned. var shape = function (config) { var that = {}; that.name = config.name || \"\"; that

Are golang slices passed by value?

由 萝らか妹 提交于 2019-11-26 02:58:05
问题 In Golang, I am trying to make a scramble slice function for my traveling salesman problem. While doing this I noticed when I started editing the slice I gave the scramble function was different every time I passed it in. After some debugging I found out it was due to me editing the slice inside the function. But since Golang is supposed to be a \"pass by value\" language, how is this possible? https://play.golang.org/p/mMivoH0TuV I have provided a playground link to show what I mean. By

Passing values in Python [duplicate]

由 。_饼干妹妹 提交于 2019-11-26 01:52:28
问题 This question already has answers here : How do I pass a variable by reference? (26 answers) Closed 6 years ago . When you pass a collection like list, array to another function in python, does it make a copy of it, or is it just a pointer? 回答1: Python passes references-to-objects by value. Python passes references-to-objects by value (like Java), and everything in Python is an object. This sounds simple, but then you will notice that some data types seem to exhibit pass-by-value

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

由 落花浮王杯 提交于 2019-11-26 01:46:41
问题 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

Are PHP Variables passed by value or by reference?

由 邮差的信 提交于 2019-11-26 01:46:30
问题 Are PHP variables passed by value or by reference? 回答1: It's by value according to the PHP Documentation. By default, function arguments are passed by value (so that if the value of the argument within the function is changed, it does not get changed outside of the function). To allow a function to modify its arguments, they must be passed by reference. To have an argument to a function always passed by reference, prepend an ampersand ( & ) to the argument name in the function definition. <

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

由 こ雲淡風輕ζ 提交于 2019-11-26 01:42:14
问题 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

Why should I use the keyword “final” on a method parameter in Java?

由 ≯℡__Kan透↙ 提交于 2019-11-26 01:36:47
问题 I can\'t understand where the final keyword is really handy when it is used on method parameters. If we exclude the usage of anonymous classes, readability and intent declaration then it seems almost worthless to me. Enforcing that some data remains constant is not as strong as it seems. If the parameter is a primitive then it will have no effect since the parameter is passed to the method as a value and changing it will have no effect outside the scope. If we are passing a parameter by

Are arrays in PHP passed by value or by reference?

由 痞子三分冷 提交于 2019-11-26 00:58:06
问题 When an array is passed as an argument to a method or function is it passed by reference? What about doing this: $a = array(1,2,3); $b = $a; Is $b a reference to $a ? 回答1: For the second part of your question, see the array page of the manual, which states (quoting) : Array assignment always involves value copying. Use the reference operator to copy an array by reference. And the given example : <?php $arr1 = array(2, 3); $arr2 = $arr1; $arr2[] = 4; // $arr2 is changed, // $arr1 is still
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