Re: [Haskell-cafe] extending Do notation

On Tue, May 20, 2014 at 1:02 PM, Kim-Ee Yeoh wrote:

On Wed, May 21, 2014 at 2:47 AM, silvio wrote:

...

do print map (<-readFile) ["foo","bar"]

The closest current Haskell can come to this is

print =<< mapM readFile ["foo","bar"]

And I agree that the manual effect typing, the requisite =<< and the mapM for map, can be a pain.

For an example that's harder to convert, I occasionally have something like this: f x | a && (b > 1 || (c && d)) && e = ... Now if 'c' becomes monadic you have to rewrite the whole expression in an entirely different (and much noisier) style. Not just all the lifting, but you can't use infix operators anymore. It really does feel like there are two languages (or dialects), with different idioms and syntax. You can translate between them without much complicated effort, but it's still a manual translation.