def plus1(a : Int) : Int = 1 + a
it takes an argument
a
of type Int
and returns 1 + a
(you guessed it). you can call this function like plus1(2)
. [you could have enclosed the body of the function in curly braces, but it's just one expression, so you don't have to]so, now let's define a higher-order function. that's a function which takes another function as parameter or returns a function.
def doWithInt(a : Int, f : Int => Int) : Int = f(a)
this is a function that takes an
Int
as first parameter and a function type as second. the parameter f
is a function of type Int => Int
which takes an Int
as parameter and returns an Int
. this function simply applies the function f
to the parameter a
. you could call this function passing to it a reference to the function plus1
declared before: doWithInt(3, plus1)
. this will return 4
as it applies plus1
to 3
. so, these are just the basics of functional programming with scala. things can become quite weird when it comes to more complex higher-order functions, e.g. function returning functions, currying or recursion. have a look at 'Scala By Example' for examples.
one thing i forgot to mentioned is some syntactic sugar for the example above. instead of calling
doWithInt(3, plus1)
you could have equally donedoWithInt(3, 1 +)
this is because
+
is a member function of the type Int
, as seen in a previous post.so, that's it for this post then. more on functional programming with scala coming soon.
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