Scala Recursive Function with patterns

Question

When creating a function with recursion on Pattern matching its throws the below error, but when created with a method it works fine. Can you please help me understand.

val power: (Int, Int) => Int = (base: Int, exp: Int) => {
    exp match {
        case 0 => 1
        case 1 => `base`
        case e => `base` * power(`base`, e - 1) 
    }
}

The code above shows produces the error: "Forward reference extends over definition of value". But the code below works fine:

def func1(base: Int, exp: Int): Int = {
    exp match {
        case 0 => 1
        case 1 => `base`
        case e => `base` * func1(`base`, e - 1)
    }
}

I got the error when i tried to run it via Eclipse Scala Worksheet,but the same code works fine on scala REPL.Thanks jwvh — Tyrion Lannister
– Tyrion Lannister, Commented Jul 3, 2015 at 23:53
I've tested it on a Scala worksheet on IntelliJ IDEA 14 and 15EAP. It works so I guess it's just Eclipse Scala worksheet issue. — Kevin Lee
– Kevin Lee, Commented Jul 4, 2015 at 6:14

bjfletcher · Accepted Answer · 2015-07-04 00:12:51Z

2

Try adding lazy to the front of the val in order that the expression is set rather than executed. Then when it is executed by calling it, it will already have been set.

answered Jul 4, 2015 at 0:12

bjfletcher

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