want better error msg with Class Read

[Dean Herington]

On Thu, 7 Nov 2002, Johannes Waldmann wrote:

> Dear all, I would welcome some advice 
> on getting better error messages
> when using  read :: Read a => a
> 
> The problem is, `readsPrec' (the class method) 
> eats the longest feasible input prefix,
> but when I call `read' (built-in prelude function)
> on a string that does not parse, but that has a valid prefix, I get this:
> 
> > Inter> readsPrec 0 "1 ) " :: [(Integer,String)]
> > [(1," ) ")]
> > Inter> read "1 )" :: Integer
> > 
> > Program error: Prelude.read: no parse
> 
> This is correct, but I would like to show (in the error message)
> the prefix that *was* parsed as well.
> If `read' was a class method, I could override it.
> (Compare class Show, where there is the method `showsPrec',
> but since H98 (?), `show' is a class method as well.)

Why not just define your own function, much like `read`, that produces a
more suitable error message?

 -- Dean