On Thu, 28 Aug 2008, Brandon S. Allbery KF8NH wrote:
On 2008 Aug 28, at 13:21, Tim Newsham wrote:
GNU ld supports "pragmas" which cause the use of certain functions to output warnings at link time (try compiling a C program that uses gets()). It occurs to me that this, either in compiler or linker, would be a nice thing for ghc to do when using fromJust or other partial functions.
would you include all partial functions in this, such as head?
I'd like to, but IMO head is a little more acceptable because lists aren't binary like Maybe. fromJust really is the Haskell equivalent of dereferencing a pointer without checking if it's NULL, aside from being more reliably detectable.
-- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH
Tools like Neil Mitchell's Catch can do more sophisticated checking, as long as your program can be compiled by YHC. Sometimes fromJust can be quite useful, though, especially in tandem with isJust. For example,
prop_foobar :: SomeType -> Property prop_foobar x = isJust (someTypeToMaybe x) ==> fromJust x == expectedResult
Alex