anonymous-function | 易学教程

What is the context of an anonymous function?

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问题 I have code like this: function demo() { this.val=5; function() { this.val=7; }(); } Now when I give execute this code in the firefox or chrome console it gives a syntax error. I don't understand why this is an error because I have read that javascript functions are objects so when I call the anonymous function, inside it this points to function demo and should change the val to 7 , so if I do var x=new demo(); x.val; //should give 7 but when I do this function demo() { this.val=5; var f

Arguments to JavaScript Anonymous Function

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问题 for (var i = 0; i < somearray.length; i++) { myclass.foo({'arg1':somearray[i][0]}, function() { console.log(somearray[i][0]); }); } How do I pass somearray or one of its indexes into the anonymous function ? somearray is already in the global scope, but I still get somearray[i] is undefined 回答1: The i in the anonymous function captures the variable i , not its value . By the end of the loop, i is equal to somearray.length , so when you invoke the function it tries to access an non-existing

matlab constant anonymous function returns only one value instead of an array

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问题 I've been searching the net for a couple of mornings and found nothing, hope you can help. I have an anonymous function like this f = @(x,y) [sin(2*pi*x).*cos(2*pi*y), cos(2*pi*x).*sin(2*pi*y)]; that needs to be evaluated on an array of points, something like x = 0:0.1:1; y = 0:0.1:1; w = f(x',y'); Now, in the above example everything works fine, the result w is a 11x2 matrix with in each row the correct value f(x(i), y(i)). The problem comes when I change my function to have constant values:

need more explanation on w3schools javascript closure example

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问题 I'm trying to understand closures and am looking at the W3Schools javascript tutorial. This is one example they give by making a counter. <body> <p>Counting with a local variable.</p> <button type="button" onclick="myFunction()">Count!</button> <p id="demo">0</p> <script> var add = (function () { var counter = 0; return function () {return counter += 1;} })(); function myFunction(){ document.getElementById("demo").innerHTML = add(); } </script> </body> Example Explained The variable add is

Why does this wildcarded function tells me it has the wrong number of parameters?

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问题 The offending code was: <console>:47: error: wrong number of parameters; expected = 2 terms.foldLeft(r.unitA)(r.add(_, _.eval(x))) I solved my problem by writing: terms.foldLeft(r.unitA)((a,b) => r.add(a, b.eval(x))) But I'd still like to know what prevented my initial attempt? 回答1: From what I've read on this type of issue, when you use "_" as a place holder for an anonymous parameter of a function, the scope of that function is the innermost parenthesis containing it. So when you wrapped

Why is this function handle being used in the incorrect context?

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问题 I am trying to understand how to pass functions to varfun , which I suppose applies to arrayfun , cellfun etc. Reading the helpfile, the first argument should be: Function, specified as a function handle. You can define the function in a file or as an anonymous function. If func corresponds to more than one function file (that is, if func represents a set of overloaded functions), MATLAB determines which function to call based on the class of the input arguments. So I try it with the

Why is this function handle being used in the incorrect context?

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Are Chrome user-scripts separated from the global namespace like Greasemonkey scripts?

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问题 I know Greasemonkey scripts are automatically wrapped in anonymous functions isolated in some way in order to prevent them conflicting with scripts in the page. Does the same happen with Chrome user-scripts? 回答1: Yes, Greasemonkey scripts are normally wrapped in an anonymous function. And, Chrome userscripts apparently are too. But, more importantly, Greasemonkey scripts are usually 1 wrapped in an XPCNativeWrapper sandbox, while Google Chrome converts userscripts into extensions, and they

How to pass anonymous functions as parameters in Rust?

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问题 I've been playing around with Rust the past week. I can't seem to figure out how to pass a function that is defined as a parameter when calling the method, and haven't come across any documentation that shows them being used in that fashion. Is it possible to define a function in the parameter list when calling a function in Rust ? This is what I've tried so far... fn main() { // This works thing_to_do(able_to_pass); // Does not work thing_to_do(fn() { println!("found fn in indent position");

C#: Anonymous method vs Named method

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问题 I'm new to SO and programming and learning day by day with bits and pieces of tech (C#) jargons. After Googling for a while, below is what I've researched about methods A Method is a block of statements, which serves for code reusability & it also supports overloading with different SIGNATURE....for ex: drawShape(2pts), drawShape(3pts) etc... An Anonymous method is one with block of statements, but no name....(as its premature to ask, in wt situation we come across anonymous method...any