#2041: Allow splicing in concrete syntax -------------------------------------+------------------------------------- Reporter: igloo | Owner: Type: feature request | Status: new Priority: normal | Milestone: ⊥ Component: Template Haskell | Version: 6.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by ezyang): The feature as stated here is rather conservatively stated, but in a more generalized form it could greatly improve the usability of Template Haskell. Basically, you are asking for proper quote/antiquote (antiquotes are nested splices.) There's a few ways this could be implemented: 1. (Original String) As this ticket suggests, a new constructor is defined which contains bits of concrete syntax. When, converting from the TH representation to GHC representation, the GHC parser is invoked to convert syntax into concrete representation. 2. (Monadic String) Alternately, some new methods could be added to the Quasi monad, which is the "hook" interface that allows template-haskell to call into GHC's code. These methods would like in the Q monad. This has the benefit of letting us error out early if syntax is not well-formed. 3. (ghc-api) We could make splices accept proper `ghc` AST returns, in which case we skip the TH conversion pass. In this case, a user could just directly call out to the ghc-api to parse syntax, and then that could be inserted into the TH splcie. 4. (Parser) Introduce a new syntactic form for quotation (something like quasi-quote syntax? quasi-quote with a special sigil?); contents of the quotation are parsed by the parser. Some tricky stuff happens. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/2041#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler