Apply a callback to an array: Difference between revisions

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=={{header|Scala}}==

val l = List(1,2,3,4)

l.foreach {i => ~~Console.~~println(i)}

l.foreach {i => println(i)}

When the argument appears only once -as here, i appears only one in println(i) - it may be shortened to

l.foreach(println(_))

Same for an array

val a = Array(1,2,3,4)

a.foreach {i => ~~Console.~~println(i)}

a.foreach {i => println(i)}

a.foreach(println(_)) '' // same as previous line''

// Or for an externally defined function

Or for an externally defined function :

def doSomething(in: int) = {~~Console.~~println("Doing something with "+in)}

def doSomething(in: int) = {println("Doing something with "+in)}

l.foreach(doSomething)

There is also a ''for'' syntax, which is internally rewritten to call foreach. A foreach method must be define on ''a''

for(val i <- a) ~~Console.~~println(i)

for(val i <- a) println(i)

It is also possible to apply a function on each item of an list to get a new list (same on array and most collections)

val squares = l.map{i => i * i} //~~returns~~ List(1,4,9,16)

val squares = l.map{i => i * i} ''//squares is'' List(1,4,9,16)

Or the equivalent ''for'' syntax, with the additional keyword ''yield'', map is called instead of foreach