src/Tools/Haskell/Value.hs

more formal references;

{- generated by Isabelle -}

{-  Title:      Haskell/Tools/Value.hs
    Author:     Makarius
    LICENSE:    BSD 3-clause (Isabelle)

Plain values, represented as string.

See also "$ISABELLE_HOME/src/Pure/General/value.ML".
-}

module Isabelle.Value
  (print_bool, parse_bool, print_int, parse_int, print_real, parse_real)
where

import Data.Maybe
import qualified Data.List as List
import qualified Text.Read as Read


{- bool -}

print_bool :: Bool -> String
print_bool True = "true"
print_bool False = "false"

parse_bool :: String -> Maybe Bool
parse_bool "true" = Just True
parse_bool "false" = Just False
parse_bool _ = Nothing


{- int -}

print_int :: Int -> String
print_int = show

parse_int :: String -> Maybe Int
parse_int = Read.readMaybe


{- real -}

print_real :: Double -> String
print_real x =
  let s = show x in
    case span (/= '.') s of
      (a, '.' : b) | List.all (== '0') b -> a
      _ -> s

parse_real :: String -> Maybe Double
parse_real = Read.readMaybe