[darcs-users] darcs patch: shell_harness script in haskell

Jason Dagit dagit at codersbase.com
Thu Oct 30 18:42:31 UTC 2008


On Thu, Oct 30, 2008 at 8:53 AM, Christian Kellermann
<Christian.Kellermann at nefkom.net> wrote:
> Hi,
>
> This obsoletes the last patch and incorporates the set_env suggestion
> made by Jason. It is supposed to be portable for windows as well
> as it does not use the setEnv funciton from Posix anymore.
>
> As always comments and suggestions are more than welcome.

Okay, since you've opened the door for comments :)  I'll put on my
nitpickers hat and comment here.

+    let myenv =
[("HOME",cwd),("PWD",cwd),("EMAIL","tester"),("DARCSEMAIL","tester"),("PATH",(darcs_path++":"++path)),("DARCS_DONT_COLOR","1"),("DARCS_DONT_ESCAPE_ANYTHING","1")]

We don't seem to have any hard and fast rules about line length, but
this one does seem overly long.  This might be a bit easier for
people:
+    let myenv = [("HOME",cwd),("PWD",cwd),("EMAIL","tester")
+                ,("DARCSEMAIL","tester"),("PATH",(darcs_path++":"++path))
+                ,("DARCS_DONT_COLOR","1")
+                ,("DARCS_DONT_ESCAPE_ANYTHING","1")]

I think we can make this a bit simpler:
+set_env :: [(String,String)] -> [(String,String)] -> [(String, String)]
+set_env [] env = env
+set_env (e:es) env = set_env es (set_env_helper e env)
+   where set_env_helper :: (String,String) -> [(String,String)] ->
[(String, String)]
+         set_env_helper (key, val) env = nubBy (\(x,_) (y,_) -> x ==
y) ((key,val):env)

The way nubBy works is that it will remove all duplicates and we
really only need to run it once the way you've structured the code.
Untested, but I think what you've written is equivalent to this:
+set_env es env = nubBy (\(x,_) (y,_) -> x == y) (es ++ env)

By the way, have you tried using your code in place of the existing
shell_harness to see that everything works?

Thanks!
Jason


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