Malcolm Wallace wrote:
For what reasons do you require the original prelude?
Exactly the same reasons. We want to do as little desugaring as necessary in the transformation, so inevitably we need at least a small part of the Prelude in scope.
This is a bit misleading. We do desugar as far as possible anything that refers to prelude functions, e.g. list comprehensions and do notation (these constructs could still be traced specially, although currently this is not the case). However, the transformed program does contain numeric literals and according to the Haskell 98 definition a compiler will add an implicit fromInteger etc to every such literal. According to Haskell 98 this fromInteger always refers to the Prelude. We want to produce Haskell 98 code and hence do not want to rely on any non-standard -no-implicit-prelude option, but we may use it circumvent the current problem of lack of defaulting. (Our transformation does add its own TPrelude.fromInteger to every literal, but that is a separate issue). At the moment I cannot think of any other original Prelude function in a transformed program. Naturally the transformed Prelude and also our tracing combinators use the original Prelude heavily. Btw Bernie, I'm surprised you say that transforming the Prelude was no problem for you. It did take me quite a lot of time. The problem is that altough most of it is just Haskell, some parts are primitive. So the Prelude has to be split into a transformable part and a core part, the tracing version of which needs to be written by hand. Also the Prelude and some standard library modules are mutually recursive, which no Haskell compiler handles easily. Hence I defined one large module, from which both Prelude and some standard libraries import, but only export parts of it. It is also tricky to avoid recursive dependencies between core and transformable parts. Ciao, Olaf -- OLAF CHITIL, Dept. of Computer Science, The University of York, York YO10 5DD, UK. URL: http://www.cs.york.ac.uk/~olaf/ Tel: +44 1904 434756; Fax: +44 1904 432767