Update on GHC 6.12.1

[kahl at cas.mcmaster.ca]

Simon Peyton Jones answered me:

 > |  >   do { a <- getChar
 > |  >      ; rec { b <- f c
 > |  >            ; c <- g b }
 > |  >      ; putChar c
 > |  >      ; return b }
 > 
 > 
 > | This last point notwithstanding,
 > | I find the scoping rules very unintuitive!
 > | (b and c appear to escape their apparently nested scope.)
 > 
 > well you are happy with
                ^^^^^

(Let's say: I got used to it...)

 > 
 > 	do { z <- getChar
 > 	   ; let { b = f c
 >                 ; c = g b }
 >           ; putChar c
 >           ; return b }
 > 
 > It's just the same!

Indeed; I had not noticed that.
(I am spoilt by layout, and had never ``seen'' those braces before.)

However, if you write those braces, there is no reason anymore to omit the
 ``in do'' at the end! This variant of let is only motivated by layout...

Analogously, is

|  >   do { a <- getChar
|  >      ; rec { b <- f c
|  >            ; c <- g b }
|  >      ; putChar c
|  >      ; return b }

equivalent to

|  >   do { a <- getChar
|  >      ; rec { b <- f c
|  >            ; c <- g b } in do
|  >         { putChar c
|  >         ; return b }

?

Is

|  >   do { rec { b <- f c
|  >            ; c <- g b }
|  >      ; putChar c
|  >      ; return b }

equivalent to

|  >   rec { b <- f c
|  >       ; c <- g b } in do
|  >      { putChar c
|  >      ; return b }

?

Would ``dorec'', in analogy with ``letrec'', perhaps be a better name?


Wolfram