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Today's Topics:
1. Fwd: using Shake to compile c++ (David McBride)
2. Re: Fwd: using Shake to compile c++ (Roger Mason)
----------------------------------------------------------------------
Message: 1
Date: Sat, 8 Jul 2017 08:51:09 -0400
From: David McBride <toa...@gmail.com>
To: Haskell Beginners <beginners@haskell.org>
Subject: [Haskell-beginners] Fwd: using Shake to compile c++
Message-ID:
<can+tr43txen81hsdnrfanvpfzbeqwjih+p-fozvykem91xc...@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Sorry this should have been sent to the list.
---------- Forwarded message ----------
From: David McBride <toa...@gmail.com>
Date: Sat, Jul 8, 2017 at 8:49 AM
Subject: Re: [Haskell-beginners] using Shake to compile c++
To: Roger Mason <rma...@mun.ca>
There's three errors here. pkg-config is an IO action and thus in
order to use its output, you must use <- instead of a let binding.
Then you must choose what you want to save from that command. You
could get the exit result, stderr or stdout or both stdout and stderr.
We want stdout. And lastly, Stdout is parameterized over a type a,
and you have to decide which.
You can either do the following
Stdout i <- cmd "pkg-config glib-2.0 --cflags"
() <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i :: String]
Or you can enable ScopedTypeVariables and go
Stdout (i :: String) <- cmd "pkg-config glib-2.0 --cflags"
I don't really understand why Stdout is parameterized, rather than
just being forced to be a string like Stdin, that's a question for the
shake authors.
On Sat, Jul 8, 2017 at 7:57 AM, Roger Mason <rma...@mun.ca> wrote:
> David McBride <toa...@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 <toa...@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
------------------------------
Message: 2
Date: Sat, 08 Jul 2017 12:21:58 -0230
From: Roger Mason <rma...@mun.ca>
To: David McBride <toa...@gmail.com>
Cc: Haskell Beginners <beginners@haskell.org>
Subject: Re: [Haskell-beginners] Fwd: using Shake to compile c++
Message-ID: <y65y3rznfqp....@mun.ca>
Content-Type: text/plain
David McBride <toa...@gmail.com> writes:
> Sorry this should have been sent to the list.
>
> ---------- Forwarded message ----------
> From: David McBride <toa...@gmail.com>
> Date: Sat, Jul 8, 2017 at 8:49 AM
> Subject: Re: [Haskell-beginners] using Shake to compile c++
> To: Roger Mason <rma...@mun.ca>
>
>
> There's three errors here. pkg-config is an IO action and thus in
> order to use its output, you must use <- instead of a let binding.
> Then you must choose what you want to save from that command. You
> could get the exit result, stderr or stdout or both stdout and stderr.
> We want stdout. And lastly, Stdout is parameterized over a type a,
> and you have to decide which.
>
> You can either do the following
>
> Stdout i <- cmd "pkg-config glib-2.0 --cflags"
> () <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i :: String]
>
> Or you can enable ScopedTypeVariables and go
> Stdout (i :: String) <- cmd "pkg-config glib-2.0 --cflags"
>
> I don't really understand why Stdout is parameterized, rather than
> just being forced to be a string like Stdin, that's a question for the
> shake authors.
For the record, I have currently
"objects//*.o" %> \out -> do
let c = dropDirectory1 $ out -<.> "cxx"
let m = out -<.> "m"
Stdout i <- cmd "pkg-config glib-2.0 --cflags"
need i
() <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i :: String]
needMakefileDependencies m
and get
Build.hs:31:59: error:
* Couldn't match type `[Char]' with `Char'
Expected type: String
Actual type: [FilePath]
* In the expression: i :: String
In the 7th argument of `cmd', namely `[i :: String]'
In a stmt of a 'do' block:
() <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i :: String]
I thank you very much for your help but it is clear that the use of
Shake requires rather more Haskell knowledge than is implied by the
docs. Given that this is just the easy part of the build the prospects
for early success look scant so I will move on and try something else.
Thanks again,
Roger
------------------------------
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