add raisedTo method for PMMatrix (#209)

* add raisedTo method for PMMatrix
A raisedTo: anInteger method is added for PMMatrix. Now, exponentiation of matrices can be performed using this method.

* remove nested ifs by a guard clause
Some formatting changes, renaming arguments are also done

* replace recursion with iteration

Author: rakki-18

src/Math-Matrix/PMMatrix.class.st

@@ -824,6 +824,27 @@ PMMatrix >> qrFactorizationWithPivoting [
 	^ Array with: q with: r with: pivot
 ]
 
+{ #category : #operation }
+PMMatrix >> raisedTo: aPower [
+
+	" Answers the receiver raised to a power, aPower .
+	 If aPower is negative, inverse of the receiver is raised to the absolute value of aPower."
+	
+	|aRaisedPMMatrix|
+
+	self assert: self isSquare description: 'Matrix should be square'.
+	
+	aPower < 0 ifTrue: [
+		^ self inverse raisedTo: aPower abs ].
+	
+	aRaisedPMMatrix := PMMatrix identity: self numberOfRows.
+	
+	1 to: aPower do: [ :each |
+		aRaisedPMMatrix := aRaisedPMMatrix * self ].
+	
+	^ aRaisedPMMatrix 
+]
+
 { #category : #'as yet unclassified' }
 PMMatrix >> rank [ 
 	^	((self numberOfRows < self numberOfColumns 

src/Math-Tests-Matrix/PMMatrixTest.class.st

@@ -632,6 +632,56 @@ PMMatrixTest >> testPrintOn [
 	m printOn: stream
 ]
 
+{ #category : #tests }
+PMMatrixTest >> testRaisedToNegativeInteger [  
+
+	|aPMMatrix expected|
+	
+	aPMMatrix := PMMatrix rows: #(#(3 1) #(1 1)).
+	
+	aPMMatrix := aPMMatrix raisedTo: -2.
+	
+	expected := PMMatrix rows: #(#(0.5 -1) #(-1 2.5)).
+	self assert: aPMMatrix equals: expected.
+]
+
+{ #category : #tests }
+PMMatrixTest >> testRaisedToNonSquareMatrix [
+
+	|aPMMatrix|
+	
+	aPMMatrix := PMMatrix rows: #(#(3 1 4) #(1 1 2)).
+	
+	self should: [ aPMMatrix raisedTo: 3 ] raise: AssertionFailure.
+	
+]
+
+{ #category : #tests }
+PMMatrixTest >> testRaisedToPositiveInteger [ 
+
+	|aPMMatrix expected|
+	
+	aPMMatrix := PMMatrix rows: #(#(3 1) #(1 1)).
+	
+	aPMMatrix := aPMMatrix raisedTo: 3.
+	
+	expected := PMMatrix rows: #(#(34 14) #(14 6)).
+	self assert: aPMMatrix equals: expected.
+]
+
+{ #category : #tests }
+PMMatrixTest >> testRaisedToZero [
+
+	|aPMMatrix expected|
+	
+	aPMMatrix := PMMatrix rows: #(#(3 1) #(1 1)).
+	
+	aPMMatrix := aPMMatrix raisedTo: 0.
+	
+	expected := PMMatrix rows: #( #(1 0) #(0 1)).
+	self assert: aPMMatrix equals: expected.
+]
+
 { #category : #comparing }
 PMMatrixTest >> testRowsColumns [
 	| a |