git-annex/Utility/Tense.hs
Joey Hess 1ff889e456
explict export lists
A small amount of dead code removed.

All of Utility/ done now.

This commit was sponsored by Brock Spratlen on Patreon.
2019-11-23 11:24:10 -04:00

60 lines
1.5 KiB
Haskell

{- Past and present tense text.
-
- Copyright 2012 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
{-# LANGUAGE OverloadedStrings #-}
module Utility.Tense (
Tense(..),
TenseChunk(..),
TenseText,
renderTense,
tenseWords,
) where
import qualified Data.Text as T
import Data.Text (Text)
import GHC.Exts( IsString(..) )
data Tense = Present | Past
deriving (Eq)
data TenseChunk = Tensed Text Text | UnTensed Text
deriving (Eq, Ord, Show)
newtype TenseText = TenseText [TenseChunk]
deriving (Eq, Ord)
{- Allows OverloadedStrings to be used, to build UnTensed chunks. -}
instance IsString TenseChunk where
fromString = UnTensed . T.pack
{- Allows OverloadedStrings to be used, to provide UnTensed TenseText. -}
instance IsString TenseText where
fromString s = TenseText [fromString s]
renderTense :: Tense -> TenseText -> Text
renderTense tense (TenseText chunks) = T.concat $ map render chunks
where
render (Tensed present past)
| tense == Present = present
| otherwise = past
render (UnTensed s) = s
{- Builds up a TenseText, separating chunks with spaces.
-
- However, rather than just intersperse new chunks for the spaces,
- the spaces are appended to the end of the chunks.
-}
tenseWords :: [TenseChunk] -> TenseText
tenseWords = TenseText . go []
where
go c [] = reverse c
go c (w:[]) = reverse (w:c)
go c ((UnTensed w):ws) = go (UnTensed (addspace w) : c) ws
go c ((Tensed w1 w2):ws) =
go (Tensed (addspace w1) (addspace w2) : c) ws
addspace w = T.append w " "