function-literal | 易学教程

Better approach nulling variables, objects in Javascript

阅读更多关于 Better approach nulling variables, objects in Javascript

问题 I am building something for mobile and would like somehow to clear, null objects, variables to release a bit of memory. Here I have two quick examples, both are anonymous functions as I believe but what way is better or more valid approach? Sorry if I get it all wrong. To me both seem to do the same thing although I like more the first one as objects wont be created until I need it. The second version would immediately execute the code for creating variables, objects etc. but not doing the

Scala underscore use to simplify syntax of function literals

阅读更多关于 Scala underscore use to simplify syntax of function literals

问题 I have the following code: var x = Array(1,3,4,4,1,1,3) var m = Int.MaxValue x.foreach((x)=>(m = m min x)) I tried to simplify last sentence to: x.foreach((m = _ min m)) But the interpreter says: scala> x.foreach((m = _ min m)) <console>:8: error: missing parameter type for expanded function ((x$1) => x$1.min(m)) x.foreach((m = _ min m)) ^ I tried to be more explicit about the type: scala> x.foreach((m = (_:Int) min m)) <console>:8: error: type mismatch; found : (Int) => Int required: Int x

Scala underscore use to simplify syntax of function literals

阅读更多关于 Scala underscore use to simplify syntax of function literals

Multiline function literal as arguments in Scala

阅读更多关于 Multiline function literal as arguments in Scala

问题 I always wondered why sometimes with function literals we can ignore the curly brace even for multiple statements. To illustrate this, the syntax for a multiline function literal is to enclose the statements with curly braces. Like so, val fl = (x: Int) => { println("Add 25 to "+x) x + 25 } However, when you pass it to a single-argument function, you can ignore the required curly brace for the function literal. So for a given function f, def f( fl: Int => Int ) { println("Result is "+ fl(5))

Questions about placeholders in Scala

阅读更多关于 Questions about placeholders in Scala

问题 Consider the following definition in Scala: val f = ((_: Int) + 1).toString() The code assigns to f the string representation of the function literal _ + 1, which is quite natural, except that this is not i want. i intended to define a function that accepts an int argument, increments it by 1, and returns its string format. To disambiguate, i have to write a lambda expression with explicit parameters: val g = (x: Int) => (x + 1).toString() So can i conclude that the placeholder syntax is not

Exact meaning of Function literal in JavaScript

阅读更多关于 Exact meaning of Function literal in JavaScript

问题 In JavaScript there are both Object literals and function literals. Object literal: myObject = {myprop:"myValue"} Function literal: myFunction = function() { alert("hello world"); } What is the significance of the word literal? Can we say Java has method literals? public void myMethod() { System.out.println("are my literal"); } 回答1: A function literal is just an expression that defines an unnamed function. The syntax for a function literal is much like that of the function statement, except

Which languages support recursive function literals / anonymous functions?

阅读更多关于 Which languages support *recursive* function literals / anonymous functions?

问题 It seems quite a few mainstream languages support function literals these days. They are also called anonymous functions, but I don't care if they have a name. The important thing is that a function literal is an expression which yields a function which hasn't already been defined elsewhere, so for example in C, &printf doesn't count. EDIT to add: if you have a genuine function literal expression <exp> , you should be able to pass it to a function f(<exp>) or immediately apply it to an

How to define a function that takes a function literal (with an implicit parameter) as an argument?

阅读更多关于 How to define a function that takes a function literal (with an implicit parameter) as an argument?

问题 I want to be able to do something on these lines (won't compile): def logScope(logger:Logger)(operation: (implicit l:Logger) => Unit) {/* code */ operation(logger) /* code */} def operationOne(implicit logger:Logger) {/**/} def operationTwo(implicit logger:Logger) {/**/} And then use it like so: logScope(new ConsoleLogger){logger => operationOne operationTwo } But the nearest I've come to a working solution is this: def logScope(logger:Logger)(operation: Logger => Unit) {/* code */ operation

The argument types of an anonymous function must be fully known. (SLS 8.5)

阅读更多关于 The argument types of an anonymous function must be fully known. (SLS 8.5)

I have a function literal {case QualifiedType(preds, ty) => t.ty = ty ; Some((emptyEqualityConstraintSet,preds)) } Which results in an error message missing parameter type for expanded function The argument types of an anonymous function must be fully known. (SLS 8.5) Expected type was: ? => Option[(Typer.this.EqualityConstraintSet, Typer.this.TypeRelationSet)] I looked in SLS 8.5 , but didn't find an explanation. If I expand the function myself to {(qt : QualifiedType) => qt match {case QualifiedType(preds, ty) => t.ty = ty ; Some((emptyEqualityConstraintSet,preds)) }} the error goes away. (a

The argument types of an anonymous function must be fully known. (SLS 8.5)

阅读更多关于 The argument types of an anonymous function must be fully known. (SLS 8.5)

问题 I have a function literal {case QualifiedType(preds, ty) => t.ty = ty ; Some((emptyEqualityConstraintSet,preds)) } Which results in an error message missing parameter type for expanded function The argument types of an anonymous function must be fully known. (SLS 8.5) Expected type was: ? => Option[(Typer.this.EqualityConstraintSet, Typer.this.TypeRelationSet)] I looked in SLS 8.5, but didn't find an explanation. If I expand the function myself to {(qt : QualifiedType) => qt match {case