{-
Copyright (C) 2010 Dr. Alistair Ward
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see .
-}
{- |
[@AUTHOR@] Dr. Alistair Ward
[@DESCRIPTION@] Delimits a data-sequence, via its offset & length, within a wider list.
-}
module RegExDot.Span(
-- * Types
-- ** Type-synonyms
Span,
-- * Functions
after,
empty,
join
) where
import Control.Arrow((***))
import qualified RegExDot.ConsumptionBounds as ConsumptionBounds
{- |
* The offset & length of a specific data-sequence, within a wider list.
* Similar to .
-}
type Span = (ConsumptionBounds.DataLength {-offset-}, ConsumptionBounds.DataLength)
-- | An empty instance, located at the specified offset.
empty :: ConsumptionBounds.DataLength -> Span
empty offset = (offset, 0)
-- | Returns the furthest extent, i.e. the offset just after the end.
after :: Span -> ConsumptionBounds.DataLength
after = uncurry (+)
{- |
* Condenses a list into a single value.
* Expects a gap-free, sorted list.
-}
join
:: ConsumptionBounds.DataLength -- ^ The offset into the list of input-data to use when a null list of spans is received.
-> [Span]
-> Span
join offset [] = empty offset -- The offset can't be deduced from a null list, so use the value provided.
join _ [singleton] = singleton -- Merely for efficiency.
join _ spanList = head *** sum $ unzip spanList