They are subsets of xs: xs1 is the variables used by c, while xs2 is the variables used by ss but not bound in p. So the command 'c' gets local environment xs1 and stack (). The translations of statements are arrows

#7828: RebindableSyntax and Arrow ----------------------------------------------+---------------------------- Reporter: AlessandroVermeulen | Owner: Type: bug | jstolarek Priority: normal | Status: new Component: Compiler (Type checker) | Milestone: 7.10.1 Resolution: | Version: 7.6.2 Operating System: Unknown/Multiple | Keywords: Type of failure: GHC rejects valid program | Architecture: Test Case: | Unknown/Multiple Blocking: | Difficulty: Unknown | Blocked By: | Related Tickets: ----------------------------------------------+---------------------------- Comment (by jstolarek): that

take an environment (here xs2) as input.

That starts to make sense :-) As I understand `x1` and `x2` need not be disjoint - is that correct? I am yet to understand the rules for encoding the input parameters to the arrows. Is there a general rule that says when and in what order things are put on the stack? Is it the case that elements on the stack are never accessed and need to be popped if they are to be used? I know all of this could be deduced from the source code, but sadly this is not straightforward (at least for me).

I don't understand that question - I don't see a bind expression in the generated code.

What I meant is that desugaring of arrow bind is completely different from monadic bind (which is desugared to `>>=`+lambda) so perhaps it deserves its own internal representation. But in fact this is what my prototype implements ie. it distingushes arrow and monadic bind. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7828#comment:22 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler