2017-04-16 14:37 GMT+02:00 Vassil Ognyanov Keremidchiev <varosi@gmail.com>:

A small proposition for the next standard.

I think every proposal should clearly state the problem it is trying to solve first, because only after there's some agreement that it is actually a problem, further discussion is useful.

1) It is to lower verbosity with omitting 'let' keyword in do-notation and use only (=) for describing let/pure blocks. [...]

As has been discussed quite a few times on this and other Haskell-related lists, "verbosity" is a very subjective measure, and the number of characters to type is one of the worst metrics for evaluating the usefulness of a feature.

In our example at hand, "let" is a very useful syntactic cue, and the visual difference between "x = foo" and "x <- foo" is a bit low IMHO. One can probably remove a lot of other syntactic stuff from Haskell and still keep it parsable by machines, but I think that's a non-goal. Remember that e.g. the entropy of English text is around 1 bit per character, but we don't speak binary, for a good reason. :-)

2) Second proposition is every pure expression ('let') in do-block to have visibility in whole block, just like top-level function is visible in whole module. Currently there is difference in visibility depending on that if a function is in do-block or is outside it.

I think the difference is there for a good reason: The desugaring rules are easy to comprehend. With your proposal things get complicated. Take e.g. a slightly modified version of your example (which can easily be complicated much more by alternating the different forms of bindings):

main = do
z <- action x
x = expression1 y
y = expression2 z

putStrLn (x ++ y ++ z)

What is the meaning of this? And what problem exactly is this part of the proposal trying to solve?