Forgive me if this has already been asked elsewhere. I have a Scala syntax question involving function-values and implicit parameters.
I'm comfortable using implicits with Scala's currying feature. For instance if I had a sum function and wanted to make the second argument an implicit:
scala> def sum(a: Int)(implicit b: Int) = a + b
sum: (a: Int)(implicit b: Int)Int
Is there a way to do this using the function-value syntax? Ignoring the implicit for a moment, I typically write curried function-values like this:
scala> val sum2 = (a: Int) => (b: Int) => a + b
sum: (Int) => (Int) => Int = <function1>
However, the function signature in the second approach is much different (the currying is being expressed explicitly). Just adding the implicit keyword to b doesn't make much sense and the compiler complains as well:
scala> val sum2 = (a: Int) => (implicit b: Int) => a + b
<console>:1: error: '=>' expected but ')' found.
val sum2 = (a: Int) => (implicit b: Int) => a + b
^
Furthermore partially-applying sum from the very first approach to get a function-value causes problems as well:
scala> val sumFunction = sum _
<console>:14: error: could not find implicit value for parameter b: Int
val sumFunction = sum _
^
This leads me to believe that functions that have implicit parameters must have said parameters determined when the function-value is created, not when the function-value is applied later on. Is this really the case? Can you ever use an implicit parameter with a function-value?
Thanks for the help!