[Haskell-cafe] trouble compiling "import
GHC.Prim(MutableByteArray#, ....." (building regex-tdfa from
darcs) -- what's that # sign doing?
stefanor at cox.net
Fri Aug 17 16:47:57 EDT 2007
On Fri, Aug 17, 2007 at 04:27:29PM -0400, Thomas Hartman wrote:
> trying to compile regex-tdfa, I ran into another issue. (earlier I had a
> cabal problem but that's resolved.)
> there's a line that won't compile, neither for ghc 6.6.1 nor 6.7
> so the fresh darcs regex tdfa package won't build.
> This line (line 16 below) causes this error for
> ghc -e '' RunMutState.hs
> for both ghc 6.1 and 6.7
There are at least two things going on here.
1. GHC-specific unboxed identifiers have a # in the name. I think this
is a relic from back when the only reasonable way to namespace was to
modify your compiler to add extra identifier characters, and use them
in all non-portable identifiers. In any case, you have to enable the
-fglasgow-exts option (or -XMagicHash in recent 6.7) to allow imports
of such identifiers.
2. Explicitly importing GHC.Prim has been discouraged for as long as I
can remember, and GHC HQ has finally made good on the promise to make
it impossible. Code which imports it has a bug already, which can be
fixed by switching to GHC.Exts. (Why? GHC.Prim is wired into the
compiler, while GHC.Exts is a normal Haskell module, so by using
GHC.Exts you are insulated from questions of what is primitive and
what is derived but still unportable. Yes, this does change.)
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