Scala implicit conversions with multiple arguments [duplicate]

Question

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How can implicits with multiple inputs be used in Scala? (2 answers)

Closed 8 years ago.

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?

Answer 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.