swap <[]> and <{}> syntax

[ghc-hetmet.git] / compiler / utils / FastBool.lhs

diff --git a/compiler/utils/FastBool.lhs b/compiler/utils/FastBool.lhs
index d7776e4..32cb7ae 100644 (file)
--- a/compiler/utils/FastBool.lhs
+++ b/compiler/utils/FastBool.lhs
@@ -5,6 +5,7 @@
 
 \begin{code}
 module FastBool (
+    --fastBool could be called bBox; isFastTrue, bUnbox; but they're not
     FastBool, fastBool, isFastTrue, fastOr, fastAnd
   ) where
 
@@ -12,25 +13,57 @@ module FastBool (
 
 -- Import the beggars
 import GHC.Exts
-       ( Int(..), Int#, (+#), (-#), (*#), 
-         quotInt#, negateInt#, (==#), (<#), (<=#), (>=#), (>#)
-       )
+#ifdef DEBUG
 import Panic
+#endif
 
 type FastBool = Int#
 fastBool True  = 1#
 fastBool False = 0#
-isFastTrue x = x ==# 1#
+
+#ifdef DEBUG
+--then waste time deciding whether to panic. FastBool should normally
+--be at least as fast as Bool, one would hope...
+
+isFastTrue 1# = True
+isFastTrue 0# = False
+isFastTrue _ = panic "FastTypes: isFastTrue"
 
 -- note that fastOr and fastAnd are strict in both arguments
 -- since they are unboxed
 fastOr 1# _ = 1#
 fastOr 0# x = x
-fastOr _  _ = panic# "FastTypes: fastOr"
+fastOr _  _ = panicFastInt "FastTypes: fastOr"
 
 fastAnd 0# _ = 0#
 fastAnd 1# x = x
-fastAnd _  _ = panic# "FastTypes: fastAnd"
+fastAnd _  _ = panicFastInt "FastTypes: fastAnd"
+
+--these "panicFastInt"s (formerly known as "panic#") rely on
+--FastInt = FastBool ( = Int# presumably),
+--haha, true enough when __GLASGOW_HASKELL__.  Why can't we have functions
+--that return _|_ be kind-polymorphic ( ?? to be precise ) ?
+
+#else /* ! DEBUG */
+--Isn't comparison to zero sometimes faster on CPUs than comparison to 1?
+-- (since using Int# as _synonym_ fails to guarantee that it will
+--   only take on values of 0 and 1)
+isFastTrue 0# = False
+isFastTrue _ = True
+
+-- note that fastOr and fastAnd are strict in both arguments
+-- since they are unboxed
+-- Also, to avoid incomplete-pattern warning
+-- (and avoid wasting time with redundant runtime checks),
+-- we don't pattern-match on both 0# and 1# .
+fastOr 0# x = x
+fastOr _  _ = 1#
+
+fastAnd 0# _ = 0#
+fastAnd _  x = x
+
+#endif /* ! DEBUG */
+
 
 #else /* ! __GLASGOW_HASKELL__ */