[Haskell-cafe] let vs do?

[Arie Peterson]

Dave Bayer wrote:

> [...] In the Haskell do expression, every line is equally special,
> and type information is used to combine the lines, inserting implied
> combinators.[...]

Desugaring do-notation is a syntactic transformation, requiring no type
information. (In practice, the parts may be required to have a monadic
type, but this is only to get an earlier (hence better) error message, I
guess.)

> I see potential for a whole language that worked
> this way, opened up to let the programmers control this process
> without waiting for an implementation to take their suggestions
> (think history of arrows) piecemeal.

How would you propose to specify such transformations?


Greetings,

Arie