Menu
I noticed that when I'm working with functions that expect other functions as parameters, I can sometimes do this:
someFunction(firstParam,anotherFunction) But other times, the compiler is giving me an error, telling me that I should write a function like this, in order for it to treat it as a partially applied function:
someFunction(firstParam,anotherFunction _) For example, if I have this:
object Whatever { def meth1(params:Array[Int]) = ... def meth2(params:Array[Int]) = ... } import Whatever._ val callbacks = Array(meth1 _,meth2 _) Why can't I have the code like the following:
val callbacks = Array(meth1,meth2) Under what circumstances will the compiler tell me to add _?
706
The Partially applied functions are the functions which are not applied on all the arguments defined by the stated function i.e, while invoking a function, we can supply some of the arguments and the left arguments are supplied when required.
Advantages of Currying Function in Scala One benefit is that Scala currying makes creating anonymous functions easier. Scala Currying also makes it easier to pass around a function as a first-class object. You can keep applying parameters when you find them.
Currying is the process of converting a function with multiple arguments into a sequence of functions that take one argument. Each function returns another function that consumes the following argument.
Syntax. def functionName ([list of parameters]) : [return type] = { function body return [expr] } Here, return type could be any valid Scala data type and list of parameters will be a list of variables separated by comma and list of parameters and return type are optional.
The rule is actually simple: you have to write the _ whenever the compiler is not explicitly expecting a Function object.
Example in the REPL:
scala> def f(i: Int) = i f: (i: Int)Int scala> val g = f <console>:6: error: missing arguments for method f in object $iw; follow this method with `_' if you want to treat it as a partially applied function val g = f ^ scala> val g: Int => Int = f g: (Int) => Int = <function1> If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
