1 % -----------------------------------------------------------------------------
2 % $Id: Enum.lhs,v 1.4 2001/07/04 11:29:26 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 import Data.Tuple () -- for dependencies
25 default () -- Double isn't available yet
29 %*********************************************************
31 \subsection{Class declarations}
33 %*********************************************************
37 minBound, maxBound :: a
43 enumFrom :: a -> [a] -- [n..]
44 enumFromThen :: a -> a -> [a] -- [n,n'..]
45 enumFromTo :: a -> a -> [a] -- [n..m]
46 enumFromThenTo :: a -> a -> a -> [a] -- [n,n'..m]
48 succ = toEnum . (`plusInt` oneInt) . fromEnum
49 pred = toEnum . (`minusInt` oneInt) . fromEnum
50 enumFrom x = map toEnum [fromEnum x ..]
51 enumFromThen x y = map toEnum [fromEnum x, fromEnum y ..]
52 enumFromTo x y = map toEnum [fromEnum x .. fromEnum y]
53 enumFromThenTo x1 x2 y = map toEnum [fromEnum x1, fromEnum x2 .. fromEnum y]
55 -- Default methods for bounded enumerations
56 boundedEnumFrom :: (Enum a, Bounded a) => a -> [a]
57 boundedEnumFrom n = map toEnum [fromEnum n .. fromEnum (maxBound `asTypeOf` n)]
59 boundedEnumFromThen :: (Enum a, Bounded a) => a -> a -> [a]
60 boundedEnumFromThen n1 n2
61 | i_n2 >= i_n1 = map toEnum [i_n1, i_n2 .. fromEnum (maxBound `asTypeOf` n1)]
62 | otherwise = map toEnum [i_n1, i_n2 .. fromEnum (minBound `asTypeOf` n1)]
69 %*********************************************************
73 %*********************************************************
76 instance Bounded () where
80 instance Enum () where
81 succ _ = error "Prelude.Enum.().succ: bad argment"
82 pred _ = error "Prelude.Enum.().pred: bad argument"
84 toEnum x | x == zeroInt = ()
85 | otherwise = error "Prelude.Enum.().toEnum: bad argument"
89 enumFromThen () () = [()]
90 enumFromTo () () = [()]
91 enumFromThenTo () () () = [()]
95 instance (Bounded a, Bounded b) => Bounded (a,b) where
96 minBound = (minBound, minBound)
97 maxBound = (maxBound, maxBound)
99 instance (Bounded a, Bounded b, Bounded c) => Bounded (a,b,c) where
100 minBound = (minBound, minBound, minBound)
101 maxBound = (maxBound, maxBound, maxBound)
103 instance (Bounded a, Bounded b, Bounded c, Bounded d) => Bounded (a,b,c,d) where
104 minBound = (minBound, minBound, minBound, minBound)
105 maxBound = (maxBound, maxBound, maxBound, maxBound)
109 %*********************************************************
111 \subsection{Type @Bool@}
113 %*********************************************************
116 instance Bounded Bool where
120 instance Enum Bool where
122 succ True = error "Prelude.Enum.Bool.succ: bad argment"
125 pred False = error "Prelude.Enum.Bool.pred: bad argment"
127 toEnum n | n == zeroInt = False
129 | otherwise = error "Prelude.Enum.Bool.toEnum: bad argment"
131 fromEnum False = zeroInt
132 fromEnum True = oneInt
134 -- Use defaults for the rest
135 enumFrom = boundedEnumFrom
136 enumFromThen = boundedEnumFromThen
139 %*********************************************************
141 \subsection{Type @Ordering@}
143 %*********************************************************
146 instance Bounded Ordering where
150 instance Enum Ordering where
153 succ GT = error "Prelude.Enum.Ordering.succ: bad argment"
157 pred LT = error "Prelude.Enum.Ordering.pred: bad argment"
159 toEnum n | n == zeroInt = LT
162 toEnum _ = error "Prelude.Enum.Ordering.toEnum: bad argment"
164 fromEnum LT = zeroInt
168 -- Use defaults for the rest
169 enumFrom = boundedEnumFrom
170 enumFromThen = boundedEnumFromThen
173 %*********************************************************
175 \subsection{Type @Char@}
177 %*********************************************************
180 instance Bounded Char where
182 maxBound = '\x10FFFF'
184 instance Enum Char where
186 | not (ord# c# ==# 0x10FFFF#) = C# (chr# (ord# c# +# 1#))
187 | otherwise = error ("Prelude.Enum.Char.succ: bad argument")
189 | not (ord# c# ==# 0#) = C# (chr# (ord# c# -# 1#))
190 | otherwise = error ("Prelude.Enum.Char.pred: bad argument")
195 {-# INLINE enumFrom #-}
196 enumFrom (C# x) = eftChar (ord# x) 0x10FFFF#
197 -- Blarg: technically I guess enumFrom isn't strict!
199 {-# INLINE enumFromTo #-}
200 enumFromTo (C# x) (C# y) = eftChar (ord# x) (ord# y)
202 {-# INLINE enumFromThen #-}
203 enumFromThen (C# x1) (C# x2) = efdChar (ord# x1) (ord# x2)
205 {-# INLINE enumFromThenTo #-}
206 enumFromThenTo (C# x1) (C# x2) (C# y) = efdtChar (ord# x1) (ord# x2) (ord# y)
208 eftChar = eftCharList
209 efdChar = efdCharList
210 efdtChar = efdtCharList
214 "eftChar" forall x y. eftChar x y = build (\c n -> eftCharFB c n x y)
215 "efdChar" forall x1 x2. efdChar x1 x2 = build (\ c n -> efdCharFB c n x1 x2)
216 "efdtChar" forall x1 x2 l. efdtChar x1 x2 l = build (\ c n -> efdtCharFB c n x1 x2 l)
217 "eftCharList" eftCharFB (:) [] = eftCharList
218 "efdCharList" efdCharFB (:) [] = efdCharList
219 "efdtCharList" efdtCharFB (:) [] = efdtCharList
223 -- We can do better than for Ints because we don't
224 -- have hassles about arithmetic overflow at maxBound
225 {-# INLINE eftCharFB #-}
226 eftCharFB c n x y = go x
229 | otherwise = C# (chr# x) `c` go (x +# 1#)
231 eftCharList x y | x ># y = []
232 | otherwise = C# (chr# x) : eftCharList (x +# 1#) y
235 -- For enumFromThenTo we give up on inlining
237 | delta >=# 0# = go_up_char_fb c n x1 delta 0x10FFFF#
238 | otherwise = go_dn_char_fb c n x1 delta 0#
243 | delta >=# 0# = go_up_char_list x1 delta 0x10FFFF#
244 | otherwise = go_dn_char_list x1 delta 0#
248 efdtCharFB c n x1 x2 lim
249 | delta >=# 0# = go_up_char_fb c n x1 delta lim
250 | otherwise = go_dn_char_fb c n x1 delta lim
254 efdtCharList x1 x2 lim
255 | delta >=# 0# = go_up_char_list x1 delta lim
256 | otherwise = go_dn_char_list x1 delta lim
260 go_up_char_fb c n x delta lim
263 go_up x | x ># lim = n
264 | otherwise = C# (chr# x) `c` go_up (x +# delta)
266 go_dn_char_fb c n x delta lim
269 go_dn x | x <# lim = n
270 | otherwise = C# (chr# x) `c` go_dn (x +# delta)
272 go_up_char_list x delta lim
275 go_up x | x ># lim = []
276 | otherwise = C# (chr# x) : go_up (x +# delta)
278 go_dn_char_list x delta lim
281 go_dn x | x <# lim = []
282 | otherwise = C# (chr# x) : go_dn (x +# delta)
286 %*********************************************************
288 \subsection{Type @Int@}
290 %*********************************************************
292 Be careful about these instances.
293 (a) remember that you have to count down as well as up e.g. [13,12..0]
294 (b) be careful of Int overflow
295 (c) remember that Int is bounded, so [1..] terminates at maxInt
297 Also NB that the Num class isn't available in this module.
300 instance Bounded Int where
304 instance Enum Int where
306 | x == maxBound = error "Prelude.Enum.succ{Int}: tried to take `succ' of maxBound"
307 | otherwise = x `plusInt` oneInt
309 | x == minBound = error "Prelude.Enum.pred{Int}: tried to take `pred' of minBound"
310 | otherwise = x `minusInt` oneInt
315 {-# INLINE enumFrom #-}
316 enumFrom (I# x) = eftInt x 2147483647#
317 -- Blarg: technically I guess enumFrom isn't strict!
319 {-# INLINE enumFromTo #-}
320 enumFromTo (I# x) (I# y) = eftInt x y
322 {-# INLINE enumFromThen #-}
323 enumFromThen (I# x1) (I# x2) = efdInt x1 x2
325 {-# INLINE enumFromThenTo #-}
326 enumFromThenTo (I# x1) (I# x2) (I# y) = efdtInt x1 x2 y
330 efdtInt = efdtIntList
333 "eftInt" forall x y. eftInt x y = build (\ c n -> eftIntFB c n x y)
334 "efdInt" forall x1 x2. efdInt x1 x2 = build (\ c n -> efdIntFB c n x1 x2)
335 "efdtInt" forall x1 x2 l. efdtInt x1 x2 l = build (\ c n -> efdtIntFB c n x1 x2 l)
337 "eftIntList" eftIntFB (:) [] = eftIntList
338 "efdIntList" efdIntFB (:) [] = efdIntList
339 "efdtIntList" efdtIntFB (:) [] = efdtIntList
343 {-# INLINE eftIntFB #-}
344 eftIntFB c n x y | x ># y = n
347 go x = I# x `c` if x ==# y then n else go (x +# 1#)
348 -- Watch out for y=maxBound; hence ==, not >
349 -- Be very careful not to have more than one "c"
350 -- so that when eftInfFB is inlined we can inline
351 -- whatver is bound to "c"
353 eftIntList x y | x ># y = []
356 go x = I# x : if x ==# y then [] else go (x +# 1#)
359 -- For enumFromThenTo we give up on inlining; so we don't worry
360 -- about duplicating occurrences of "c"
361 efdtIntFB c n x1 x2 y
362 | delta >=# 0# = if x1 ># y then n else go_up_int_fb c n x1 delta lim
363 | otherwise = if x1 <# y then n else go_dn_int_fb c n x1 delta lim
369 | delta >=# 0# = if x1 ># y then [] else go_up_int_list x1 delta lim
370 | otherwise = if x1 <# y then [] else go_dn_int_list x1 delta lim
376 | delta >=# 0# = go_up_int_fb c n x1 delta ( 2147483647# -# delta)
377 | otherwise = go_dn_int_fb c n x1 delta ((-2147483648#) -# delta)
382 | delta >=# 0# = go_up_int_list x1 delta ( 2147483647# -# delta)
383 | otherwise = go_dn_int_list x1 delta ((-2147483648#) -# delta)
387 -- In all of these, the (x +# delta) is guaranteed not to overflow
389 go_up_int_fb c n x delta lim
392 go_up x | x ># lim = I# x `c` n
393 | otherwise = I# x `c` go_up (x +# delta)
395 go_dn_int_fb c n x delta lim
398 go_dn x | x <# lim = I# x `c` n
399 | otherwise = I# x `c` go_dn (x +# delta)
401 go_up_int_list x delta lim
404 go_up x | x ># lim = [I# x]
405 | otherwise = I# x : go_up (x +# delta)
407 go_dn_int_list x delta lim
410 go_dn x | x <# lim = [I# x]
411 | otherwise = I# x : go_dn (x +# delta)