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author | Sylvain Henry <sylvain@haskus.fr> | 2021-05-27 15:53:25 +0200 |
---|---|---|
committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-05-28 15:32:44 -0400 |
commit | df997fac54bbadd399593f49228b6292e71145f1 (patch) | |
tree | 8977d9b8b897b1760436ce75df7a0cbea2d6bbc3 /libraries/base/GHC/Show.hs | |
parent | f74204c4f6f3f386c9688ca45a893f68894ecacd (diff) | |
download | haskell-df997fac54bbadd399593f49228b6292e71145f1.tar.gz |
Use quotRemWord in showWord
Using the following high-quality benchmark (with -O2):
main :: IO ()
main = do
let
go 0 = ""
go n@(W# n#) = showWord n# (go (n -1))
print $ length (go 10000000)
I get the following performance results:
- remWord+quotRem: 0,76s user 0,00s system 99% cpu 0,762 total
- quotRemWord: 0,45s user 0,01s system 99% cpu 0,456 total
Note that showSignedInt already uses quotRemInt.
Diffstat (limited to 'libraries/base/GHC/Show.hs')
-rw-r--r-- | libraries/base/GHC/Show.hs | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/libraries/base/GHC/Show.hs b/libraries/base/GHC/Show.hs index 0d90006432..04fbcb6112 100644 --- a/libraries/base/GHC/Show.hs +++ b/libraries/base/GHC/Show.hs @@ -202,9 +202,11 @@ instance Show Word where showWord :: Word# -> ShowS showWord w# cs | isTrue# (w# `ltWord#` 10##) = C# (chr# (ord# '0'# +# word2Int# w#)) : cs - | otherwise = case chr# (ord# '0'# +# word2Int# (w# `remWord#` 10##)) of - c# -> - showWord (w# `quotWord#` 10##) (C# c# : cs) + | otherwise = + let + !(# q, r #) = quotRemWord# w# 10## + !c# = chr# (ord# '0'# +# word2Int# r) + in showWord q (C# c# : cs) -- | @since 2.01 deriving instance Show a => Show (Maybe a) |