I am on my way to learning Scala after coming from different programming languages (mostly interpreted). I am doing the following exercise and I get an error.
def sum(f: Int => Int)(a: Int, b: Int): Int = {
def loop(a: Int, acc: Int): Int = {
if (a >= b) acc
else loop(a+1, f(a) + acc)
}
loop(a, 0)
}
sum(x => x * x, 2, 4) //Too many arguments
I can't see what is wrong there?
If you declare your function with multiple parentheses (multiple argument lists), you also have to call it like that (curried form):
sum(x => x * x)(2, 4)
See What's the difference between multiple parameters lists and multiple parameters per list in Scala? for more information.
The function must be called in the explicitly curried form (there must be a better name) because that is how it is defined:
sum(x => x * x)(2, 4)
//def sum (f: Int => Int) (a: Int, b: Int):
// sum (x => x * x) (2, 4)
But this is also neat, because only one part of the curried form must be evaluated at a time:
val sumOfSquares = sum(x => x * x)
val s = someOfSquares(2,4)
You have defined sum with two parameter lists but are trying to call it with just one.
The syntactically correct way to call it would be sum(x => x * x)(2, 4)
