megaparsec/Text/Parsec/Pos.hs

-----------------------------------------------------------------------------
-- |
-- Module      :  Text.Parsec.Pos
-- Copyright   :  (c) Daan Leijen 1999-2001, (c) Paolo Martini 2007
-- License     :  BSD-style (see the LICENSE file)
-- 
-- Maintainer  :  paolo@nemail.it
-- Stability   :  provisional
-- Portability :  portable
-- 
-- Textual source positions.
-- 
-----------------------------------------------------------------------------

module Text.Parsec.Pos
    ( SourceName, Line, Column
    , SourcePos
    , sourceLine, sourceColumn, sourceName
    , incSourceLine, incSourceColumn
    , setSourceLine, setSourceColumn, setSourceName
    , newPos, initialPos
    , updatePosChar, updatePosString
    ) where

-- | Source positions: a file name, a line and a column
-- upper left is (1,1)

type SourceName = String
type Line       = Int
type Column     = Int

data SourcePos  = SourcePos SourceName !Line !Column
    deriving ( Eq, Ord )

newPos :: SourceName -> Line -> Column -> SourcePos
newPos sourceName line column
    = SourcePos sourceName line column

initialPos :: SourceName -> SourcePos
initialPos sourceName
    = newPos sourceName 1 1

sourceName :: SourcePos -> SourceName
sourceName (SourcePos name line column) = name

sourceLine :: SourcePos -> Line
sourceLine (SourcePos name line column) = line

sourceColumn :: SourcePos -> Column
sourceColumn (SourcePos name line column) = column

incSourceLine :: SourcePos -> Line -> SourcePos
incSourceLine (SourcePos name line column) n = SourcePos name (line+n) column

incSourceColumn :: SourcePos -> Column -> SourcePos
incSourceColumn (SourcePos name line column) n = SourcePos name line (column+n)

setSourceName :: SourcePos -> SourceName -> SourcePos
setSourceName (SourcePos name line column) n = SourcePos n line column

setSourceLine :: SourcePos -> Line -> SourcePos
setSourceLine (SourcePos name line column) n = SourcePos name n column

setSourceColumn :: SourcePos -> Column -> SourcePos
setSourceColumn (SourcePos name line column) n = SourcePos name line n

-- | Update source positions on characters

updatePosString :: SourcePos -> String -> SourcePos
updatePosString pos string
    = forcePos (foldl updatePosChar pos string)

updatePosChar   :: SourcePos -> Char -> SourcePos
updatePosChar pos@(SourcePos name line column) c
    = forcePos $
      case c of
        '\n' -> SourcePos name (line+1) 1
        '\t' -> SourcePos name line (column + 8 - ((column-1) `mod` 8))
        _    -> SourcePos name line (column + 1)

forcePos :: SourcePos -> SourcePos
forcePos pos@(SourcePos name line column)
    = seq line (seq column (pos))

-- | Show positions

instance Show SourcePos where
  show (SourcePos name line column)
    | null name = showLineColumn
    | otherwise = "\"" ++ name ++ "\" " ++ showLineColumn
    where
      showLineColumn    = "(line " ++ show line ++
                          ", column " ++ show column ++
                          ")"