Scala阶乘语法错误

Question

I wrote the following code:

def factorial(x: Int, factorial( x => { if (x == 0) 1 else x * factorial(x - 1) })): Int = factorial(3)

But got the error:

<console>:1: error: ':' expected but '(' found.

Answer 1

This part of the code makes sense (syntactically, at least):

def factorial(...): Int = factorial(3)

What goes in the ... are the function's arguments. You were starting off fine with x:Int

def factorial(x: Int, ...): Int = factorial(3)

But then it kind of goes off the rails syntactically with factorial(x=>{if(x==0)1 else x*factorial(x-1)}) . I don't really know what to say about that, except that it's definitely not a function argument. That's an expression , which is the sort of thing you'd put in the function body (after the = ), not in an argument list.

Answer 2

You have factorial as a param item for your def, that is incorrect. Try:

def factorial(x:Int): Int =
  if (x == 0) 1
  else x * factorial(x - 1)