+ Most user-level Haskell types and functions provided by GHC (in + particular those from the Prelude and GHC's Prelude extensions) are + internally constructed from even more elementary types and functions. + Most notably, GHC understands a notion of unboxed types, which + are the Haskell representation of primitive bit-level integer, float, + etc. types (as opposed to their boxed, heap allocated counterparts) - + cf. "Unboxed + Values as First Class Citizens." + +
+ The hardwired types of GHC are brought into scope by the module
+ PrelGHC. This modules only exists in the form of a
+ handwritten interface file PrelGHC.hi-boot,
+ which lists the type and function names, as well as instance
+ declarations. The actually types of these names as well as their
+ implementation is hardwired into GHC. Note that the names in this file
+ are z-encoded, and in particular, identifiers ending on zh
+ denote user-level identifiers ending in a hash mark (#),
+ which is used to flag unboxed values or functions operating on unboxed
+ values. For example, we have Char#, ord#, and
+ so on.
+
+
+ As of (about) the development version 4.11, the types and various
+ properties of primitive operations are defined in the file primops.txt.pp.
+ (Personally, I don't think that the .txt suffix is really
+ appropriate, as the file is used for automatic code generation; the
+ recent addition of .pp means that the file is now mangled
+ by cpp.)
+
+ The utility genprimopcode
+ generates a series of Haskell files from primops.txt, which
+ encode the types and various properties of the primitive operations as
+ compiler internal data structures. These Haskell files are not complete
+ modules, but program fragments, which are included into compiler modules
+ during the GHC build process. The generated include files can be found
+ in the directory fptools/ghc/compiler/ and carry names
+ matching the pattern primop-*.hs-incl. They are generate
+ during the execution of the boot target in the
+ fptools/ghc/ directory. This scheme significantly
+ simplifies the maintenance of primitive operations.
+
+ As of development version 5.02, the primops.txt file also allows the
+ recording of documentation about intended semantics of the primitives. This can
+ be extracted into a latex document (or rather, into latex document fragments)
+ via an appropriate switch to genprimopcode. In particular, see primops.txt
+ for full details of how GHC is configured to cope with different machine word sizes.
+
+ +Last modified: Mon Nov 26 18:03:16 EST 2001 + + + +