Re: [Haskell-cafe] Throwback of inferred types

On Sun, 2008-01-20 at 21:02 +0000, Jon Harrop wrote:

On Sunday 20 January 2008 21:02:04 gwern0@gmail.com wrote:

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On 2008.01.19 19:11:13 +0100, Peter Verswyvelen scribbled 1.4K characters:

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I would find it most useful to get type inference information on the fly, even when not all of the code compiles correctly yet.

Does that make sense? If the code doesn't compile, then how could any type-inference be trustable?

Note that this functionality continues to be widely used in other functional languages, e.g. SML, OCaml, F#. I can't think why Haskell would be any different.

Really? That's pretty cool. How does it work? Does it use Achim's suggestion of replacing expressions which fail to type with new type vars and at runtime an error message with the type error? Or do they use something more hacky that we could also implement quickly? like: foo = 3 bar = 'c' baz = foo + bar So we infer: foo :: Int foo = 3 bar :: Char bar = 'c' baz :: a baz = error "No instance for (Num Char) arising from a use of `+' at foo.hs:5:6-14" That would be cool. Then I can run the bits of my program that still work. It'd make the editor/interpreter session rather more "live". How close do the IDEs/emacs-modes for SML, OCaml, F# come to that? What are we missing out on? :-) Duncan