[Shootout-list] Clean nsieve-bits

[Diederik van Arkel]

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A Clean version of nsieve-bits...

regards,

Diederik van Arkel


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// The Great Computer Language Shootout
// http://shootout.alioth.debian.org/
//
// contributed by Diederik van Arkel

module nsieve_bits

import StdEnv, LanguageShootout

Start world
	# n				= argi
	# (io,world)	= stdio world
	# io			= sieve n io
	# io			= sieve (n-1) io
	# io			= sieve (n-2) io
	# (err,world)	= fclose io world
	= world

nbits		:== 32
all_true	:== 0xFFFFFFFF

sieve n io
	# m		= (1 << n) * 10000
	  arr	= createArray ((m+1)/nbits + 1) all_true
	  c		= loop arr m 2 0
	= io <<< "Primes up to " <<< fmt 8 m <<< " " <<< fmt 8 c <<< "\n"

fmt width i
	# is	= toString i
	= toString (repeatn (width - size is) ' ') +++ is

loop :: !*{#Int} !Int !Int !Int -> Int
loop arr m n c
	| n == m
		= c
	| arr.[n >> 5] bitand (1 << (n bitand 31)) <> 0
		# arr	= update` arr (n+n)
		= loop arr m (n+1) (c+1)
	= loop arr m (n+1) c
where
	update` :: !*{#Int} !Int -> *{#Int}
	update` arr i
		| i <= m
			#! inb	= i >> 5
			   arri	= arr.[inb]
			   arr	= {arr & [inb] = arri bitand (bitnot (1 << (i bitand 31)))}
			= update` arr (i+n)
		= arr

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