Scala Tutorials - Basic Scala Tutorial
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13 Anonymous Functions 2

  • The first example is a method definition as we’ve seen before

  • The second, is like the previous slide, only assigned to a val, this is very, very roughly like the difference between

    function foo(x, y) { 
    return x + y; 
}

    and

    var foo = function(x, y) { 
    return x + y; 
}

    in JavaScript.

  • The third, was briefly demonstrated in the previous slide, uses the shorter _ placeholder syntax. However the usage on the left is rare in Scala, the _ notation for anonymous functions is mostly useful when passing them as parameter to higher order functions (functions that recieve or return other functions)
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def add1(x:Int, y:Int) = x + y //method
1
val add2 = (x:Int, y:Int) => x + y //anonymous function
2
val add3:(Int,Int)=>Int = _ + _ //alternate way
3
val add4 = (_ + _):(Int,Int)=>Int //alternate way, rare  
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println(add1(42,13))
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println(add2(42,13))
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println(add3(42,13))
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println(add4(42,13))
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