[EMAIL PROTECTED] wrote:
Jules Bean <[EMAIL PROTECTED]> wrote,
concerning the problem of getting at the types of local definitions:
> Simon Peyton-Jones wrote:
> The principal difficulties here are to do with "what do we want"
> rather the implementation challenges.
>
> > 1. Should the compiler print the type of every declaration? Should GHCi
allow you to ask the type of a local decl?
> >
>
> IMO, ghci should definitely allow you to ask. This comes up for me every
> time that I write any haskell code (and in general I end up hoisting
> local definitions to the top level, which is a real pain if there is
> local scope, data or type, to hoist with it).
>
> > 2. How should the variables be identified? There may be many local bindings for 'f', so you can't say just ":t f". Ditto if dumping all local bindings.
> >
> >
>
> I think this is a hard question. I was imagining some kind of
> hierarchical system like foo.f, in the case that f is locally defined
> inside foo. (Yes I know we can't easily use '.' for that). There might
> be might be multiple fs inside the definition of foo; indeed there might
> even be multiple fs nested inside each other.
I just wanted to contribute a PRACTICAL TRICK I use:
* If the local definition is a pattern binding
f = ...
then I just add
f :: Ordering
* If the local definition is a, say binary, function binding
f p1 p2 = ...
then I just add
f :: Float -> Double -> Ordering
(Type does not matter for the number of function arrows you need to put;
only the syntactic arity of the bindings matters here.)
This relies on the fact that the types Float, Double, and Ordering
very rarely occur in my code --- pick your own.
Why not just declare a type you don't use?
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