[Haskell-cafe] Turtle library : grepping on Text vs FilePath

Joe Hillenbrand joehillen at gmail.com
Wed Jun 7 23:05:56 UTC 2017

Line is not just a wrapper around Text. It's a guarantee that the
string does not contain any newline characters.

Can you be more explicit about what you are trying to do? I'm having
troubling understanding what you want. Are you trying to filter the
output of `ls` using `grep`?

For that you can do this:

main = do
  view $ grep (suffix "hs") $ fmap (unsafeTextToLine . format fp) (ls ".")

This will print all the files in the current directory that end in "hs".

On Wed, Jun 7, 2017 at 12:22 AM, Ruben Astudillo <ruben.astud at gmail.com> wrote:
> On 07/06/17 03:08, Joe Hillenbrand wrote:
>> Is onFiles[1] what you're looking for?
>> https://hackage.haskell.org/package/turtle-1.3.5/docs/Turtle-Prelude.html#v:onFiles
> Almost. Grep operates over Shell Line. Line is just a newtype over Text.
> I still don't know if this is telling me "don't do that".
>> On Tue, Jun 6, 2017 at 10:16 PM, Ruben Astudillo <ruben.astud at gmail.com> wrote:
>>> Dear list
>>> On the Turtle library, the grep function got the following signature
>>>     grep :: Pattern a -> Shell Line -> Shell Line
>>> For it to filter output of the `ls :: FilePath -> Shell FilePath` I got
>>> to fmap and transform via de Turtle.Format or Turtle.Line modules. Is
>>> this an indicator I shouldn't be doing this? Is the library telling me
>>> to use `find`? or is just accidental?
>>> --
>>> -- Ruben
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> --
> -- Ruben

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