1 % -----------------------------------------------------------------------------
2 % $Id: Enum.lhs,v 1.3 2001/07/03 14:13:32 simonmar Exp $
4 % (c) The University of Glasgow, 1992-2000
7 \section[GHC.Bounded]{Module @GHC.Bounded@}
9 Instances of Bounded for various datatypes.
12 {-# OPTIONS -fno-implicit-prelude #-}
15 Bounded(..), Enum(..),
16 boundedEnumFrom, boundedEnumFromThen,
18 -- Instances for Bounded and Eum: (), Char, Int
22 import {-# SOURCE #-} GHC.Err ( error )
24 default () -- Double isn't available yet
28 %*********************************************************
30 \subsection{Class declarations}
32 %*********************************************************
36 minBound, maxBound :: a
42 enumFrom :: a -> [a] -- [n..]
43 enumFromThen :: a -> a -> [a] -- [n,n'..]
44 enumFromTo :: a -> a -> [a] -- [n..m]
45 enumFromThenTo :: a -> a -> a -> [a] -- [n,n'..m]
47 succ = toEnum . (`plusInt` oneInt) . fromEnum
48 pred = toEnum . (`minusInt` oneInt) . fromEnum
49 enumFrom x = map toEnum [fromEnum x ..]
50 enumFromThen x y = map toEnum [fromEnum x, fromEnum y ..]
51 enumFromTo x y = map toEnum [fromEnum x .. fromEnum y]
52 enumFromThenTo x1 x2 y = map toEnum [fromEnum x1, fromEnum x2 .. fromEnum y]
54 -- Default methods for bounded enumerations
55 boundedEnumFrom :: (Enum a, Bounded a) => a -> [a]
56 boundedEnumFrom n = map toEnum [fromEnum n .. fromEnum (maxBound `asTypeOf` n)]
58 boundedEnumFromThen :: (Enum a, Bounded a) => a -> a -> [a]
59 boundedEnumFromThen n1 n2
60 | i_n2 >= i_n1 = map toEnum [i_n1, i_n2 .. fromEnum (maxBound `asTypeOf` n1)]
61 | otherwise = map toEnum [i_n1, i_n2 .. fromEnum (minBound `asTypeOf` n1)]
68 %*********************************************************
72 %*********************************************************
75 instance Bounded () where
79 instance Enum () where
80 succ _ = error "Prelude.Enum.().succ: bad argment"
81 pred _ = error "Prelude.Enum.().pred: bad argument"
83 toEnum x | x == zeroInt = ()
84 | otherwise = error "Prelude.Enum.().toEnum: bad argument"
88 enumFromThen () () = [()]
89 enumFromTo () () = [()]
90 enumFromThenTo () () () = [()]
94 instance (Bounded a, Bounded b) => Bounded (a,b) where
95 minBound = (minBound, minBound)
96 maxBound = (maxBound, maxBound)
98 instance (Bounded a, Bounded b, Bounded c) => Bounded (a,b,c) where
99 minBound = (minBound, minBound, minBound)
100 maxBound = (maxBound, maxBound, maxBound)
102 instance (Bounded a, Bounded b, Bounded c, Bounded d) => Bounded (a,b,c,d) where
103 minBound = (minBound, minBound, minBound, minBound)
104 maxBound = (maxBound, maxBound, maxBound, maxBound)
108 %*********************************************************
110 \subsection{Type @Bool@}
112 %*********************************************************
115 instance Bounded Bool where
119 instance Enum Bool where
121 succ True = error "Prelude.Enum.Bool.succ: bad argment"
124 pred False = error "Prelude.Enum.Bool.pred: bad argment"
126 toEnum n | n == zeroInt = False
128 | otherwise = error "Prelude.Enum.Bool.toEnum: bad argment"
130 fromEnum False = zeroInt
131 fromEnum True = oneInt
133 -- Use defaults for the rest
134 enumFrom = boundedEnumFrom
135 enumFromThen = boundedEnumFromThen
138 %*********************************************************
140 \subsection{Type @Ordering@}
142 %*********************************************************
145 instance Bounded Ordering where
149 instance Enum Ordering where
152 succ GT = error "Prelude.Enum.Ordering.succ: bad argment"
156 pred LT = error "Prelude.Enum.Ordering.pred: bad argment"
158 toEnum n | n == zeroInt = LT
161 toEnum _ = error "Prelude.Enum.Ordering.toEnum: bad argment"
163 fromEnum LT = zeroInt
167 -- Use defaults for the rest
168 enumFrom = boundedEnumFrom
169 enumFromThen = boundedEnumFromThen
172 %*********************************************************
174 \subsection{Type @Char@}
176 %*********************************************************
179 instance Bounded Char where
181 maxBound = '\x10FFFF'
183 instance Enum Char where
185 | not (ord# c# ==# 0x10FFFF#) = C# (chr# (ord# c# +# 1#))
186 | otherwise = error ("Prelude.Enum.Char.succ: bad argument")
188 | not (ord# c# ==# 0#) = C# (chr# (ord# c# -# 1#))
189 | otherwise = error ("Prelude.Enum.Char.pred: bad argument")
194 {-# INLINE enumFrom #-}
195 enumFrom (C# x) = eftChar (ord# x) 0x10FFFF#
196 -- Blarg: technically I guess enumFrom isn't strict!
198 {-# INLINE enumFromTo #-}
199 enumFromTo (C# x) (C# y) = eftChar (ord# x) (ord# y)
201 {-# INLINE enumFromThen #-}
202 enumFromThen (C# x1) (C# x2) = efdChar (ord# x1) (ord# x2)
204 {-# INLINE enumFromThenTo #-}
205 enumFromThenTo (C# x1) (C# x2) (C# y) = efdtChar (ord# x1) (ord# x2) (ord# y)
207 eftChar = eftCharList
208 efdChar = efdCharList
209 efdtChar = efdtCharList
213 "eftChar" forall x y. eftChar x y = build (\c n -> eftCharFB c n x y)
214 "efdChar" forall x1 x2. efdChar x1 x2 = build (\ c n -> efdCharFB c n x1 x2)
215 "efdtChar" forall x1 x2 l. efdtChar x1 x2 l = build (\ c n -> efdtCharFB c n x1 x2 l)
216 "eftCharList" eftCharFB (:) [] = eftCharList
217 "efdCharList" efdCharFB (:) [] = efdCharList
218 "efdtCharList" efdtCharFB (:) [] = efdtCharList
222 -- We can do better than for Ints because we don't
223 -- have hassles about arithmetic overflow at maxBound
224 {-# INLINE eftCharFB #-}
225 eftCharFB c n x y = go x
228 | otherwise = C# (chr# x) `c` go (x +# 1#)
230 eftCharList x y | x ># y = []
231 | otherwise = C# (chr# x) : eftCharList (x +# 1#) y
234 -- For enumFromThenTo we give up on inlining
236 | delta >=# 0# = go_up_char_fb c n x1 delta 0x10FFFF#
237 | otherwise = go_dn_char_fb c n x1 delta 0#
242 | delta >=# 0# = go_up_char_list x1 delta 0x10FFFF#
243 | otherwise = go_dn_char_list x1 delta 0#
247 efdtCharFB c n x1 x2 lim
248 | delta >=# 0# = go_up_char_fb c n x1 delta lim
249 | otherwise = go_dn_char_fb c n x1 delta lim
253 efdtCharList x1 x2 lim
254 | delta >=# 0# = go_up_char_list x1 delta lim
255 | otherwise = go_dn_char_list x1 delta lim
259 go_up_char_fb c n x delta lim
262 go_up x | x ># lim = n
263 | otherwise = C# (chr# x) `c` go_up (x +# delta)
265 go_dn_char_fb c n x delta lim
268 go_dn x | x <# lim = n
269 | otherwise = C# (chr# x) `c` go_dn (x +# delta)
271 go_up_char_list x delta lim
274 go_up x | x ># lim = []
275 | otherwise = C# (chr# x) : go_up (x +# delta)
277 go_dn_char_list x delta lim
280 go_dn x | x <# lim = []
281 | otherwise = C# (chr# x) : go_dn (x +# delta)
285 %*********************************************************
287 \subsection{Type @Int@}
289 %*********************************************************
291 Be careful about these instances.
292 (a) remember that you have to count down as well as up e.g. [13,12..0]
293 (b) be careful of Int overflow
294 (c) remember that Int is bounded, so [1..] terminates at maxInt
296 Also NB that the Num class isn't available in this module.
299 instance Bounded Int where
303 instance Enum Int where
305 | x == maxBound = error "Prelude.Enum.succ{Int}: tried to take `succ' of maxBound"
306 | otherwise = x `plusInt` oneInt
308 | x == minBound = error "Prelude.Enum.pred{Int}: tried to take `pred' of minBound"
309 | otherwise = x `minusInt` oneInt
314 {-# INLINE enumFrom #-}
315 enumFrom (I# x) = eftInt x 2147483647#
316 -- Blarg: technically I guess enumFrom isn't strict!
318 {-# INLINE enumFromTo #-}
319 enumFromTo (I# x) (I# y) = eftInt x y
321 {-# INLINE enumFromThen #-}
322 enumFromThen (I# x1) (I# x2) = efdInt x1 x2
324 {-# INLINE enumFromThenTo #-}
325 enumFromThenTo (I# x1) (I# x2) (I# y) = efdtInt x1 x2 y
329 efdtInt = efdtIntList
332 "eftInt" forall x y. eftInt x y = build (\ c n -> eftIntFB c n x y)
333 "efdInt" forall x1 x2. efdInt x1 x2 = build (\ c n -> efdIntFB c n x1 x2)
334 "efdtInt" forall x1 x2 l. efdtInt x1 x2 l = build (\ c n -> efdtIntFB c n x1 x2 l)
336 "eftIntList" eftIntFB (:) [] = eftIntList
337 "efdIntList" efdIntFB (:) [] = efdIntList
338 "efdtIntList" efdtIntFB (:) [] = efdtIntList
342 {-# INLINE eftIntFB #-}
343 eftIntFB c n x y | x ># y = n
346 go x = I# x `c` if x ==# y then n else go (x +# 1#)
347 -- Watch out for y=maxBound; hence ==, not >
348 -- Be very careful not to have more than one "c"
349 -- so that when eftInfFB is inlined we can inline
350 -- whatver is bound to "c"
352 eftIntList x y | x ># y = []
355 go x = I# x : if x ==# y then [] else go (x +# 1#)
358 -- For enumFromThenTo we give up on inlining; so we don't worry
359 -- about duplicating occurrences of "c"
360 efdtIntFB c n x1 x2 y
361 | delta >=# 0# = if x1 ># y then n else go_up_int_fb c n x1 delta lim
362 | otherwise = if x1 <# y then n else go_dn_int_fb c n x1 delta lim
368 | delta >=# 0# = if x1 ># y then [] else go_up_int_list x1 delta lim
369 | otherwise = if x1 <# y then [] else go_dn_int_list x1 delta lim
375 | delta >=# 0# = go_up_int_fb c n x1 delta ( 2147483647# -# delta)
376 | otherwise = go_dn_int_fb c n x1 delta ((-2147483648#) -# delta)
381 | delta >=# 0# = go_up_int_list x1 delta ( 2147483647# -# delta)
382 | otherwise = go_dn_int_list x1 delta ((-2147483648#) -# delta)
386 -- In all of these, the (x +# delta) is guaranteed not to overflow
388 go_up_int_fb c n x delta lim
391 go_up x | x ># lim = I# x `c` n
392 | otherwise = I# x `c` go_up (x +# delta)
394 go_dn_int_fb c n x delta lim
397 go_dn x | x <# lim = I# x `c` n
398 | otherwise = I# x `c` go_dn (x +# delta)
400 go_up_int_list x delta lim
403 go_up x | x ># lim = [I# x]
404 | otherwise = I# x : go_up (x +# delta)
406 go_dn_int_list x delta lim
409 go_dn x | x <# lim = [I# x]
410 | otherwise = I# x : go_dn (x +# delta)