Re: ghc should be able to deduce correct use of partial functions and not give a warning in such cases
Andrew Lelechenko <[email protected]>
| Newsgroups | gmane.comp.lang.haskell.cafe |
|---|---|
| Message-ID | <[email protected]> |
Hi George, If you do not want to pattern match on `ys`, the simplest solution is to do what the GHC warning suggests you to do and use `drop 1` instead of `tail`. Another alternative is `Data.List.uncons` followed by `Data.Maybe.maybe`. Best regards, Andrew > On 20 Apr 2024, at 13:28, George Colpitts <[email protected]> wrote: > > Thanks for everybody's replies > > To give more context the original code from Ch. 12 of Bird's Thinking Functionally with Haskell was: > > let (xs, ys) = break (== ch) str in > if null ys then [] else [(xs, tail ys)]) > > I replaced it with > > let (xs, ys@(_ : t)) = break (== ch) str in > if null ys then [] else [(xs, t)]) > > On Tue, Apr 16, 2024 at 10:51 AM George Colpitts <[email protected] <mailto:[email protected]>> wrote: >> ghc should be able to deduce correct use of partial functions and not give a warning in such cases, e.g. in 9.8.2 >> >> if null ys then [] else [(xs,tail ys)]) >> >> gets a warning >> >> warning: [GHC-63394] [-Wx-partial] >> >> but it is clear that this use of tail will never be a problem so IMHO that line of code should not get a warning. >> >> Does anybody know if there is a plan or enhancement request to eliminate such warnings? >> >> Cheers >> George >> >> >> >> > _______________________________________________ > Haskell-Cafe mailing list > To (un)subscribe, modify options or view archives go to: > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > Only members subscribed via the mailman list are allowed to post. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.