Extract boxMullerTransform to be more intuition revealing

Author: SergeStinckwich

src/Math-Core-Distribution/PMNormalDistribution.class.st

@@ -11,6 +11,19 @@ Class {
 	#category : #'Math-Core-Distribution'
 }
 
+{ #category : #information }
+PMNormalDistribution class >> boxMullerTransform [
+|v1 v2 w y|
+			[ v1 := Number random * 2 - 1.
+			v2 := Number random * 2 - 1.
+			w := v1 squared + v2 squared.
+			w > 1 ] whileTrue.
+			y := (w ln * 2 negated / w) sqrt.
+			v1 := y * v1.
+			NextRandom := y * v2.
+			^v1.
+]
+
 { #category : #information }
 PMNormalDistribution class >> distributionName [
 
@@ -42,17 +55,11 @@ PMNormalDistribution class >> new: aNumber1 sigma: aNumber2 [
 PMNormalDistribution class >> random [
 	"Answer a random number distributed according to a (0,1) normal distribution."
 
-	| v1 v2 w y |
+	| v1  |
 	NextRandom
 		ifNil: [
-			"Use Box-Muller transform"
-			[ v1 := Number random * 2 - 1.
-			v2 := Number random * 2 - 1.
-			w := v1 squared + v2 squared.
-			w > 1 ] whileTrue.
-			y := (w ln * 2 negated / w) sqrt.
-			v1 := y * v1.
-			NextRandom := y * v2 ]
+			
+			v1 := self boxMullerTransform ]
 		ifNotNil: [ v1 := NextRandom.
 			NextRandom := nil ].
 	^ v1