On 8/9/05, Simon Marlow
------------------ build-depends: ghc? (ghc >= 6.4, [ghc64] | ghc >= 5.04, [ghc-old]) | hugs? [hugs], debug? (HUnit-1.0, [debug]) [release], gnome? ( libglade >= 2, gtksourceview >= 0.6, gconf >= 2, [gnome] ), mozilla? ( mozilla >= 1.4, [mozilla] ), doc? ( haddock >= 0.6 )
[gnome] extra-libraries: gnome extra-ghc-options: -DENABLE_GNOME ...
[debug] extra-ghc-options: -O0 -DDEBUG
[release] extra-ghc-options: -O2
As described, it seems like I would need to pass "--enable-hugs" or "--enable-ghc" explicitly, or else this program's build would fail. But, I don't think that is your intention; instead you are intending for Cabal to automatically enable these flags as appropriate, right? Perhaps there would be other automatic flags too, like "windows" and "unix"? I think there is too much overloading being used: 1. "ghc" refers to both a flag and a package 2. "debug," "release," and "gnome," are flags and configurations. If I pass "--enable-gnome" as a flag then the "gnome" configuration gets used, if I pass "--enable-release" then the "release" configuration gets used, etc.. But, if I pass "--enable-ghc64" as a flag then the ghc64 configuration will not be used, right? Will the "--enable-ghc64" just be silently ignored? It would be nice to be able to catch typos like "--enable-debgu" What is the difference between the following?: ghc? (ghc >= 6.4, [ghc64] | ghc >= 5.04, [ghc-old]) | hugs? [hugs], vs. ( ghc >= 6.4, [ghc64] | ghc >= 5.04, [ghc-old] | hugs, [hugs] | ) vs. ghc >= 6.4, [ghc64] | ghc >= 5.04, [ghc-old] | hugs, [hugs] My understanding is that the first two are equivalent but the third one additional means "fail if building with anything other than GHC >= 5.04 or hugs," assuming that Cabal automatically enables the flags "ghc" or "hugs" appropriately. Am I correct? "a, b" means "require a and b." But, "a, [b]" means "require dependency a and use configuration b" or, equivalently "if dependency a is satisfied, then automatically use configuration b." I think it would be better to avoid overloading the comma operator with these two meanings. Can configurations contain their own "Build-depends", like this?: [windows] Build-depends: Win32 extra-libraries: gnome It seems counterintuitive to allow "extra-libraries" but to disallow "build-depends." Yet, we may want to prohibit the build-depends flag from including other configurations syntax, to prevent cycles and non-intuitive behavior: Build-depends: windows? [windows] [windows] Build-Depends: Win32, wxHaskell [gui] | extra-libraries: gdi32 [gui] Build-Depends: wxHaskell, (Win32 [windows] | ) I think it would be clearer to specify the configuration seperately, like this: configuration: ghc >= 6.4 ? [ghc64] | ghc >= 5.04 ? [ghc-old]) | hugs? [hugs], debug enabled ? [debug] | [release], gnome enabled ? [gnome], mozilla enabled ? [mozilla], doc enabled ? [doc] -- the "global" Build-depends applies to everything Build-depends: base >= 1.0, haskell98 >= 1.0 [gnome] Build-Depends: libglade >= 2, gtksourceview >= 0.6, gconf >= 2, extra-libraries: gnome extra-ghc-options: -DENABLE_GNOME [debug] Build-depends: HUnit-1.0 extra-ghc-options: -O0 -DDEBUG [release] extra-ghc-options: -O2 [mozilla] Build-depends: mozilla >= 1.4 [doc] Build-depends: haddock >= 0.6 Notice here that the "Build-Depends:" syntax would remain the same as in Cabal 1.0, as [stanza] and the "?" operator would only be allowed in "configuration:". Also notice that this requires that dependencies be allowed as the left operand of the "?" operator, but they would no longer be allowed as the right operand; only stanza names are allowed. Finally, are you intending to allow multiple executable stanzas inside configurations?: Build-depends: wxHaskell, [gui] | [gui] Executable: admin-gui Main-Is: AdminGui.hs Executable: another-gui Main-Is: AnotherGui.hs Regards, Brian