[Haskell-cafe] Ported a Python script for use with Go to Haskell

Matt Joiner anacrolix at gmail.com
Sat Apr 5 16:17:52 UTC 2014

I considered the same thing with an existing GOBIN env var. I did actually
test it and found it worked as expected. Items earlier in the list seem to
have higher priority. I prefer not to use setenv, because I want to exec
into the binary later without GOBIN clobbered, which means keeping the
current environment pristine. Good point about it not matching the Python
version, but then a few other things don't either now. :)

Here's the latest version: http://pastebin.com/EejABjpR

Something I can't get my head around: On line 50-52, I have a function that
returns the result of getting the current directory (curDir) joined with
the package path (maybeToList package). Is there someway to get the current
directory without having to store the action the way that I am doing? <$>
would work if the current directory was the last argument to the joinPath,
but here it's the first.

Thanks so much for your help.

On Sun, Apr 6, 2014 at 2:48 AM, Andrew Gibiansky <andrew.gibiansky at gmail.com
> wrote:

> The script itself looks pretty good to me, but you might want to take a
> look at Shelly <https://hackage.haskell.org/package/shelly> [0] for
> Haskell scripting in the future. It's a really nice library / DSL for
> "bash"-like scripting directly in Haskell. If you try out Shelly, I suggest
> trying it with ClassyPrelude and -XOverloadedStrings, which makes dealing
> with all the Text and FilePath types bearable. (Heh, though it's annoying,
> having FilePath as a separate type once prevented me from writing code that
> deleted my home directory upon being run... fun story.)
> [0] https://hackage.haskell.org/package/shelly
> On Sat, Apr 5, 2014 at 4:33 AM, Kim-Ee Yeoh <ky3 at atamo.com> wrote:
>> On Sat, Apr 5, 2014 at 5:21 PM, Robert Vollmert <rvollmert-lists at gmx.net>wrote:
>>> - clobbering the environment by prepending to an association list makes
>>> me wonder if that’s really what happens when the variable is already defined
>> Yes, that does raise flags.
>> The haskell here:
>>     installEnv <- getEnvironment >>= return . (:) ("GOBIN", gOBIN)
>> which I'd probably write as
>>     installEnv <- (("GOBIN", gOBIN) :) <$> getEnvironment
>> doesn't match the python here:
>>     GOBIN = tempfile.gettempdir()
>>     os.environ['GOBIN'] = GOBIN
>> in the sense that the case for a predefined GOBIN in the environment will
>> lead to different results. At least I'll be surprised if otherwise.
>> To Matt: have you tested your haskell version? You might want to take a
>> look at System.Posix.Env.putenv.
>> -- Kim-Ee
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