Ix - Library Documentation
Part of the LibraryDocumentation project.
Controls indexing, typically used in conjunction with ?LibraryDocumentation/Array.
module Ix ( Ix(range, index, inRange), rangeSize ) where
class (Ord a) => Ix a where
range :: (a,a) -> [a]
index :: (a,a) -> a -> Int
inRange :: (a,a) -> a -> Bool
rangeSize :: Ix a => (a,a) -> Int
rangeSize b@(l,h) | null (range b) = 0
| otherwise = index b h + 1
-- NB: replacing "null (range b)" by "l > h" fails if
-- the bounds are tuples. For example,
-- (2,1) > (1,2),
-- but
-- range ((2,1),(1,2)) = []
instance Ix Char where
range (m,n) = [m..n]
index b@(c,c') ci
| inRange b ci = fromEnum ci - fromEnum c
| otherwise = error "Ix.index: Index out of range."
inRange (c,c') i = c <= i && i <= c'
instance Ix Int where
range (m,n) = [m..n]
index b@(m,n) i
| inRange b i = i - m
| otherwise = error "Ix.index: Index out of range."
inRange (m,n) i = m <= i && i <= n
instance Ix Integer where
range (m,n) = [m..n]
index b@(m,n) i
| inRange b i = fromInteger (i - m)
| otherwise = error "Ix.index: Index out of range."
inRange (m,n) i = m <= i && i <= n
instance (Ix a,Ix b) => Ix (a, b) -- as derived, for all tuples
instance Ix Bool -- as derived
instance Ix Ordering -- as derived
instance Ix () -- as derived