Hal, OK. If you want to change CoreSyn.Note to have an extra constructor, thus: data Note = SCC CostCentre | Coerce Type Type | InlineMe | InlineCall | NoteString String -- NEW and check that the rest of the compiler does something sensible with NoteString, I do not object. There are only 12 lines of the compiler than mention InlineCall, for example, so I expect NoteString would be similarly low-impact. [Incidentally, InlineCall is an undocumented feature. You can write inline f x to mean the same as (f x), except that this particular call to f will be inlined.] Simon | -----Original Message----- | From: Alastair Reid [mailto:alastair@reid-consulting-uk.ltd.uk] | Sent: 06 February 2003 11:28 | To: Simon Peyton-Jones | Cc: Hal Daume III; GHC Users Mailing List | Subject: Re: ghc feature request: core notes | | | "Hal Daume III" writes: | > I'm not sure how "generally useful" this would be, but I would | > find it useful to be able to attach notes to core expressions from | > the Haskell code. The idea being something along the lines of a | > code annotation like a pragma. [...] | | Simon Peyton-Jones writes: | > [...] There is an annotation facility in Core, but it's easy for the notes | > to be discarded. So if they are conveying important info, it might | > easily get lost... and if not, what's it doing there in the first | > place. What do you expect to happen to these annotations? [...] | | It seems like _scc_ is (almost) exactly what you need here. When used | for profiling, you mark subexpressions you want profiled and ghc takes | care to preserve and propagate them in a semantically meaningful way. | Any _scc_ annotations that ghc chooses to drop can be reported as | bugs :-) | | I say "almost" because what the semantics used when profiling may not | be the right ones for your purposes. (I'm being vague because I don't | know your purposes.) | | Naturally, you'd want to be able to use these notes independently of | profiling - which can probably be done with a little preprocessor | hackery. Assuming that the 1st argument to 'NOTE' is a literal string | in the following: | | #ifdef TRACK_NOTES | #define NOTE(x,y) (_scc_ "" (y)) | #else | #define NOTE(x,y) {- nothing -} | #endif | | -- | Alastair Reid