--- a/Integer.st Mon Jan 19 14:45:59 2009 +0100
+++ b/Integer.st Mon Jan 19 14:46:12 2009 +0100
@@ -2147,7 +2147,6 @@
! !
-
!Integer methodsFor:'misc math'!
acker:n
@@ -3278,14 +3277,41 @@
"return true if I am a prime Number.
This is a q&d hack, which may need optimization if heavily used."
- |limit|
+ |limit firstFewPrimes|
self even ifTrue:[^ self == 2 ].
+ self == 1 ifTrue:[^ false ].
+
limit := self sqrt.
- 3 to:limit by:2 do:[:i |
+
+ "/ primes up to 1000
+ firstFewPrimes := #(
+ 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
+ 101 103 107 109 113 127 131 137 139 149 151 157 163 167 173 179 181 191
+ 193 197 199 211 223 227 229 233 239 241 251 257 263 269 271 277 281 283
+ 293 307 311 313 317 331 337 347 349 353 359 367 373 379 383 389 397 401
+ 409 419 421 431 433 439 443 449 457 461 463 467 479 487 491 499 503 509
+ 521 523 541 547 557 563 569 571 577 587 593 599 601 607 613 617 619 631
+ 641 643 647 653 659 661 673 677 683 691 701 709 719 727 733 739 743 751
+ 757 761 769 773 787 797 809 811 821 823 827 829 839 853 857 859 863 877
+ 881 883 887 907 911 919 929 937 941 947 953 967 971 977 983 991 997).
+
+ firstFewPrimes do:[:p |
+ p > limit ifTrue:[^ true].
+ (self \\ p) == 0 ifTrue:[ ^ false ].
+ ].
+
+ (firstFewPrimes last+2) to:limit by:2 do:[:i |
(self \\ i) == 0 ifTrue:[ ^ false ].
].
^ true
+
+ "
+ Integer primesUpTo:1000
+ (1 to:1000000) count:[:n | n isPrime] 78498
+ Time millisecondsToRun:[ (1 to:1000000) count:[:n | n isPrime]] 1295 w.o firstFewPrimes
+ Time millisecondsToRun:[ (1 to:1000000) count:[:n | n isPrime]] 936 with firstFewPrimes (less tests)
+ "
!
nextPrime
@@ -3584,7 +3610,7 @@
!Integer class methodsFor:'documentation'!
version
- ^ '$Header: /cvs/stx/stx/libbasic/Integer.st,v 1.203 2009-01-16 16:22:32 cg Exp $'
+ ^ '$Header: /cvs/stx/stx/libbasic/Integer.st,v 1.204 2009-01-19 13:46:12 cg Exp $'
! !
Integer initialize!