We need type annotations..
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Key: LS-617
URL: http://dev.sourcefabric.org/browse/LS-617
Project: Liquidsoap
Issue Type: New Feature
Affects Versions: 1.0
Reporter: Romain Beauxis
Priority: Blocker
Here's why:
# def apply(f, x) = f(x=x) end;;
apply : (((x:'a)->'b),'a)->'b = <fun>
# def optional(~x="f") = "f" end;;
optional : (?x:string)->string = fun (~x="f") -> "f"
# apply(optional, "foo");;
At line 316, char -125:
this value has type
(?x:_)->_ (infered at line 316, char -139--110)
but it should be a subtype of (the type of the v
In OCaml:
# let apply f x = f ~x:x ;;
val apply : (x:'a -> 'b) -> 'a -> 'b = <fun>
# let optional ?(x="foo") = x;;
Warning 16: this optional argument cannot be erased.
val optional : ?x:string -> string = <fun>
# apply optional "gni";;
Error: This expression has type ?x:string -> string
but an expression was expected of type x:'a -> 'b
BUT:
# let apply (f : ?x:'a -> 'b) x = f ~x:x ;;
val apply : (?x:'a -> 'b) -> 'a -> 'b = <fun>
# apply optional "gni";;
- : string = "gni"
In case you're wondering, I have a much more useful example that cannot work
without that...
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