Extracting constructor name

[Erik Hesselink]

You can use Data.Data, and the DeriveDataTypeable extension. If you
say "deriving Typeable, Data" on your data type, you can use toConstr
to get a constructor representation. See also the documentation [1].

Erik

P.S. Shouldn't this be on -cafe?

[1] http://hackage.haskell.org/packages/archive/base/latest/doc/html/Data-Data.html

On Tue, Sep 27, 2011 at 18:40, Gracjan Polak <gracjanpolak at gmail.com> wrote:
> Hi all,
>
> To get a bit better error reporting and debugging I'd like to report constructor
> names misused. Example:
>
>
> data X = A | B Int | C String
>
>
> magic A = doSomething
> magic x = error $ "magic can only be used on A, you supplied " ++ constrName x
>
> I'm missing constrName that returns only constructor name as string, skips all
> fields (if any).
>
> --
> Gracjan
>
>
>
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