[Pkg] The Trunk: Kernel-ul.305.mcz

[commits at source.squeak.org]

Andreas Raab uploaded a new version of Kernel to project The Trunk:
http://source.squeak.org/trunk/Kernel-ul.305.mcz

==================== Summary ====================

Name: Kernel-ul.305
Author: ul
Time: 25 November 2009, 2:55:43 am
UUID: a95be01c-d87c-154b-bdc6-c582dafad80b
Ancestors: Kernel-nice.304

- added Integer >> #sqrtFloor, which returns the floor of the square root of the receiver.
- renamed Integer >> #isPrime to #isProbablyPrime.
- added Integer >> #isPrime which is implemented as a deterministic primality test
- both #isPrime and #isProbablyPrime return false for receivers <= 1 instead of raising an error

=============== Diff against Kernel-nice.304 ===============

Item was added:
+ ----- Method: Integer>>isProbablyPrime (in category 'testing') -----
+ isProbablyPrime
+ 	"See isProbablyPrimeWithK:andQ: for the algoritm description."
+ 	
+ 	| k q |
+ 	self <= 1 ifTrue: [ ^false ].
+ 	self even ifTrue: [ ^self = 2 ].
+ 	k := 1.
+ 	q := self - 1 bitShift: -1.
+ 	[ q odd ] whileFalse: [
+ 		q := q bitShift: -1.
+ 		k := k + 1 ].
+ 	25 timesRepeat: [ (self isProbablyPrimeWithK: k andQ: q) ifFalse: [ ^false ] ].
+ 	^true!

Item was added:
+ ----- Method: Integer>>sqrtFloor (in category 'mathematical functions') -----
+ sqrtFloor
+ 	"Return the integer part of the square root of self"
+ 
+ 	| guess guessSquared delta |
+ 	guess := 1 bitShift: self highBit + 1 // 2.
+ 	[
+ 		guessSquared := guess * guess.
+ 		delta := guessSquared - self // (guess bitShift: 1).
+ 		delta = 0 ] whileFalse: [
+ 			guess := guess - delta ].
+ 	guessSquared = self ifFalse: [ guess := guess - 1 ].
+ 	^guess!

Item was changed:
  ----- Method: Integer>>isPrime (in category 'testing') -----
  isPrime
- 	"See isProbablyPrimeWithK:andQ: for the algoritm description."
- 	| k q |
- 	self <= 1 ifTrue: [^self error: 'operation undefined'].
- 	self even ifTrue: [^self = 2].
- 	k := 1.
- 
- 	q := self - 1 bitShift: -1.
- 	[q odd] whileFalse: 
- 			[q := q bitShift: -1.
- 			k := k + 1].
  	
+ 	self <= 1 ifTrue: [ ^false ].
+ 	self even ifTrue: [ ^self = 2].
+ 	3 to: self sqrtFloor by: 2 do: [ :each |
+ 		self \\ each = 0 ifTrue: [ ^false ] ].
- 	25 timesRepeat: [(self isProbablyPrimeWithK: k andQ: q) ifFalse: [^false]].
  	^true!