ndmitchell:
> Hi
>
> >My last impression is that instead of using -xc it is better to write
> >programs in a debug-friendly style. For example, let g x must
> >return (Just _), but the programmer is not 100% sure that g x is free
> >of bugs. Then, instead of
> > f x = h $ fromJust $ g x
> >one needs too write
>
> There are lots of solutions I use, all of which I think are nicer than your
> one!
>
> Use a safe module:
> http://neilmitchell.blogspot.com/2006/11/library-idea-safe-library.html
> - always works, a little bit of effort (I have such a module in my
> code). You then get:
>
> f x = h $ fromJustNote "Foo.f" $ g x
On a similar note, LocH would have:
$ ./a.out
a.out: A.hs:12:20-25: Maybe.fromJust: Nothing
Given:
01 import Debug.Trace.Location
02 import qualified Data.Map as M
03 import Data.Maybe
04
05 main = do print f
06
07 f = let m = M.fromList
08 [(1,"1")
09 ,(2,"2")
10 ,(3,"3")]
11 s = M.lookup 4 m
12 in fromJustSafe assert s
13
14 fromJustSafe a s = check a (fromJust s)
So there's lots of solutions now!
-- Don
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