- The function type A => B is just an abbreviation for the class scala. Function1[A, B], which is defined as follows.
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package scala; trait Function1[A, B] { def apply(x: A): B } |
- An anonymous function such as
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(x: Int) => x * x |
is expanded to:
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new Function1[Int, Int] { def apply(x: Int) = x * x } |
- A function call, such as f(a), where f is a value of some class type, is expanded to f.apply(a)
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val f = (x: Int) => x * x; f(7) |
would be
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val f = new Function1[Int, Int] { def apply(x: Int) = x * x } f.apply(7) |
- A method such as
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def f(x: Int): Boolean = ... |
is not itself a function value.
But if f is used in a place where a Function type is expected, it is converted automatically to the function value
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(x: Int) => f(x) |
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