[Haskell-beginners] using Shake to compile c++

[Roger Mason]

David McBride <toad3k at gmail.com> writes:

> Sorry that should have been command, not command_ which is very different.
>
> On Sat, Jul 8, 2017 at 7:37 AM, David McBride <toad3k at gmail.com> wrote:
>> The easy option is to just use command instead of cmd.  Variadic
>> functions are always a little weird to type check.
>>
>> command_ [] "pkg-config" ["glib-2.0","--cflags"]
>>
>> That will *probably* solve the ambiguity in both lines, but I haven't tested.

Thank you for your replies.

This is what I have now:

 "objects//*.o" %> \out -> do
        let c = dropDirectory1 $ out -<.> "cxx"
        let m = out -<.> "m"
        let i = command [] "pkg-config" ["glib-2.0","--cflags"]
        () <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i]
        needMakefileDependencies m

That produces:

Build.hs:29:17: error:
    * Ambiguous type variable `r0' arising from a use of `command'
      prevents the constraint `(CmdResult r0)' from being solved.
      Relevant bindings include i :: Action r0 (bound at Build.hs:29:13)
      Probable fix: use a type annotation to specify what `r0' should be.
      These potential instances exist:
        instance CmdResult CmdLine
          -- Defined in `Development.Shake.Command'
        instance CmdResult CmdTime
          -- Defined in `Development.Shake.Command'
        instance CmdResult Exit -- Defined in `Development.Shake.Command'
        ...plus 9 others
        ...plus two instances involving out-of-scope types
        (use -fprint-potential-instances to see them all)
    * In the expression:
        command [] "pkg-config" ["glib-2.0", "--cflags"]
      In an equation for `i':
          i = command [] "pkg-config" ["glib-2.0", "--cflags"]
      In the expression:
        do { let c = dropDirectory1 $ out -<.> "cxx";
             let m = out -<.> "m";
             let i = command ... "pkg-config" ...;
             () <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i];
             .... }

Build.hs:30:15: error:
    * No instance for (Development.Shake.Command.Arg [Action r0])
        arising from a use of `cmd'
    * In a stmt of a 'do' block:
        () <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i]
      In the expression:
        do { let c = dropDirectory1 $ out -<.> "cxx";
             let m = out -<.> "m";
             let i = command ... "pkg-config" ...;
             () <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i];
             .... }
      In the second argument of `(%>)', namely
        `\ out
           -> do { let ...;
                   let ...;
                   .... }'

Thanks again,
Roger