Scala implicit conversions with multiple arguments [duplicate]

Question

I've always thought that Scala implicit conversions could only take one argument, and if you needed something like conversion from multiple arguments, you would use a tuple. However, I was surprised to find that Scala 2.10.3 actually accepts this (silly) definition without problem:

scala> implicit def foo(i: Int, j: Int): Int = i
foo: (i: Int, j: Int)Int

Is there any way or reason to use such a multi-argument implicit?

You could use it like this: def bar[A, B, C](a: A, b: B)(implicit f: (A, B) => C) = f(a, b), though I don't think it's useful. — senia
– senia, Commented Jan 15, 2014 at 7:43
For the record, amazing how @retronym covers the bases. Is there more than one retronym? Is it a retronym collective? — som-snytt
– som-snytt, Commented Jan 15, 2014 at 8:57
@som-snytt: In a manner of speaking... At least one of them is Tyler Durden — Kevin Wright
– Kevin Wright, Commented Jan 15, 2014 at 11:37

Kevin Wright · Accepted Answer · 2014-01-15 11:33:49Z

1

Not all implicit functions are conversions!

Any implicit function with a single argument could be used as a conversion, but that's not the only use-case for implicits.

Functions are just another type and, as such, you can specify an implicit argument as in (implicit fn: (Int, Int) => Int)

I wouldn't do this though, anything you intend to pass as an implicit should have a far more specific type that better self-documents its intended purpose.

answered Jan 15, 2014 at 11:33

Kevin Wright

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