CODEWITHSUNDEEP
scalafold
Abdul Rahman
Abdul Rahman

Reputation: 1384

Scala strange error when using foldRight with operator syntax

1 to 5 foldRight (0)(x:Int, y:Int => x+y)

I am trying to add all the values from right to left with 0 as the initial parameter. I get the following error

Int(0) does not take parameters

Can anyone explain to me what this error even means? Thanks.

Upvotes: 1

Views: 153

Answers (2)

Kim Stebel
Kim Stebel

Reputation: 42045

There are two things wrong with your code. The first is that you need to use brackets around 1 to 5, the second is the syntax of your anonymous function. You need brackets around the parameters there.

(1 to 5).foldRight(0)((x,y) => x + y)

Upvotes: -1

Gabriele Petronella
Gabriele Petronella

Reputation: 108169

It's just the parser getting "confused", so it's trying to apply (x: Int, y: Int ...) as argument of (0).

Specifically, what you're using is a scala syntactic feature that allows to use

a.f(b)

as

a f b

This works with any method that has a single parameter. However when your method has multiple parameter lists (like foldRight), you have to use extra care.

This is what the parser sees

1 to 5  foldRight (0)(x: Int, y: Int => x + y)
|__a__| |___f___| |____________b_____________|

So when evaluating b, it treats 0 as a function with (x: Int, ...) as an argument. Clearly this can't work, because "Int(0) does not take parameters".

Instead, you can use

(1 to 5).foldRight(0)((x,y) => x + y)

or even

(1 to 5).foldRight(0)(_ + _)

Upvotes: 8

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