src/English.lhs

   1 %  Copyright (C) 2008 Eric Kow
   2 %
   3 %  This program is free software; you can redistribute it and/or modify
   4 %  it under the terms of the GNU General Public License as published by
   5 %  the Free Software Foundation; either version 2, or (at your option)
   6 %  any later version.
   7 %
   8 %  This program is distributed in the hope that it will be useful,
   9 %  but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 %  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 %  GNU General Public License for more details.
  12 %
  13 %  You should have received a copy of the GNU General Public License
  14 %  along with this program; see the file COPYING.  If not, write to
  15 %  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  16 %  Boston, MA 02110-1301, USA.
  17
  18
  19 \begin{code}
  20 module English where
  21
  22 import Data.List (isSuffixOf)
  23
  24 -- | > englishNum 0 (Noun "watch") "" == "watches"
  25 --   > englishNum 1 (Noun "watch") "" == "watch"
  26 --   > englishNum 2 (Noun "watch") "" == "watches"
  27 englishNum :: Numbered n => Int -> n -> ShowS
  28 englishNum x = if x == 1 then singular else plural
  29
  30 -- | Things that have a plural and singular spelling
  31 class Numbered a where
  32   plural :: a -> ShowS
  33   singular :: a -> ShowS
  34
  35 -- | This only distinguishes between nouns with a final -ch,
  36 --   and nouns which do not.
  37 --   More irregular nouns will just need to have their own type
  38 --
  39 --   > plural (Noun "batch") "" == "batches"
  40 --   > plural (Noun "bat")   "" == "bats"
  41 --   > plural (Noun "mouse") "" == "mouses" -- :-(
  42 newtype Noun = Noun String
  43
  44 instance Numbered Noun where
  45   -- more irregular nouns will just need to have their own type
  46   plural (Noun s) | "ch" `isSuffixOf` s = showString s .  showString "es"
  47   plural (Noun s) = showString s . showChar 's'
  48   singular (Noun s) =  showString s
  49
  50 -- | > singular This (Noun "batch") "" == "this batch"
  51 --   > plural   This (Noun "batch") "" == "these batches"
  52 data This = This Noun
  53
  54 instance Numbered This where
  55   plural (This s)   = showString "these "  . plural s
  56   singular (This s) = showString "this "   . singular s
  57 \end{code}