Robert Dockins <[EMAIL PROTECTED]> writes: > On Nov 15, 2006, at 9:48 AM, Jón Fairbairn wrote: > > But instead of “blah (head [ v | (n,v) <- env, n==target ]) > > blah”, you could write > > > > blah the_v_in_scope blah > > where (the_v_in_scope:_) = [ v | (n,v) <- env, n==target ] > > Or how about.... ?? > > lookupVarible target env = > case [ v | (n,v) <- env, n==target ] of > (x:_) -> x > _ -> assert False $ "BUG: Unexpected variable out of > scope "++ (show target)++" in environment "++(show env) > > > ... lookupVariable target env .... > > > It seems to me that every possible use of a partial function > has some (possibly imagined) program invariant that > prevents it from failing. Otherwise it is downright wrong. > 'head', 'fromJust' and friends don't do anything to put > that invariant in the program text.
Hear hear. -- Jón Fairbairn [EMAIL PROTECTED] _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
