Added test cases for subtraction between scalars and vectors and sugg…

…ested quickfix (PolyMathOrg#121)

* Added Basic Scalar subtraction test

* added test for subtract PMVector from a Number

* QuickFix of the scalar subtraction with PMVector Issue

src/Math-Core/PMVector.class.st

@@ -20,7 +20,7 @@ Class {
 	#name : #PMVector,
 	#superclass : #Array,
 	#type : #variable,
-	#category : #'Math-Core'
+	#category : 'Math-Core'
 }
 
 { #category : #'instance creation' }
@@ -70,17 +70,9 @@ PMVector >> + aVectorOrNumber [
 ]
 
 { #category : #operation }
-PMVector >> - aVector [
-	"Answers the difference of the receiver with aVector."
-	| answer n |
-	answer := self class new: self size.
-	n := 0.
-	self with: aVector do:
-		[ :a :b | 
-		  n := n + 1. 
-		  answer at: n put: ( a - b).
-		].
-	^answer
+PMVector >> - aVectorOrNumber [
+	"Answers the difference of the receiver with a vector or number."
+	^ -1*aVectorOrNumber addWithVector: self
 ]
 
 { #category : #operation }

src/Math-Core/PMWeightedPoint.class.st

@@ -12,7 +12,7 @@ Class {
 		'weight',
 		'error'
 	],
-	#category : #'Math-Core'
+	#category : 'Math-Core'
 }
 
 { #category : #creation }

src/Math-Tests-Core/PMVectorTest.class.st

@@ -93,6 +93,36 @@ PMVectorTest >> testScalarProductIsCommutative [
 	self assert: (u scalarProduct: v) equals: (v scalarProduct: u)
 ]
 
+{ #category : #tests }
+PMVectorTest >> testSubFromScalar [
+	"Can we subtract PMVector from a Number?"
+
+	| num vec actual expected |
+
+	num := 4.
+	vec := #(1 2 3) asPMVector.
+
+	actual := num - vec.
+	expected := #(3 2 1) asPMVector.
+
+	self assert: actual equals: expected.
+]
+
+{ #category : #tests }
+PMVectorTest >> testSubtractScalar [
+	"Can we subtract Number from PMVector?"
+
+	| vec num actual expected |
+
+	vec := #(5 6 7) asPMVector.
+	num := 4.
+
+	actual := vec - num.
+	expected := #(1 2 3) asPMVector.
+
+	self assert: actual equals: expected.
+]
+
 { #category : #tests }
 PMVectorTest >> testTensorProduct [
 	| a b c |