On Thu, Aug 09, 2007 at 08:45:14PM +0200, Benjamin Franksen wrote:
David Roundy wrote:
Several times since reading the beginning of this discussion I've wished I had the new syntax so I could write something like:
do if predicateOnFileContents (<- readFile "foo") then ...
instead of either
do contents <- readFile "foo" if predicateOnFileContents contents then ...
or (as you'd prefer)
readFile "foo" >>= \contents -> if predicateOnFileContents contents then ...
Isn't this problem, namely being forced to name intermediate results, also solved by some sort of idiom bracket sugar, maybe together with the lambda case proposal? I would prefer both very much to the proposed (<- action) syntax for the same reasons that e.g. Jules Bean nicely summarized.
I'm not familiar with the lambda case proposal, and don't know what you mean by idiom bracket sugar, but I haven't had an idea (or heard of one) that was nearly so elegant as the (<- action) proposal, which neatly allows one to lift any existing pure function or syntactic construct (except lambda expressions?) into a monad. i.e. we don't need to define a separate 'if', 'case', etc, and we don't need liftM, liftM2, liftM3, liftM4andahalf, all of which are subsumed by a single pretty syntax. The only cost is that this syntax relies on the do notation, and thus makes the desugaring of that do notation slightly more complicated when used. -- David Roundy Department of Physics Oregon State University