"{ Package: 'stx:libbasic2' }"

"{ NameSpace: Smalltalk }"

SquareMatrix variableSubclass:#Matrix3_3

	instanceVariableNames:''

	classVariableNames:''

	poolDictionaries:''

	category:'Collections-MultiDimensional'

!

!Matrix3_3 class methodsFor:'documentation'!

documentation

"

    3x3 Matrix (2 dimensions).

    Especially useful with the ArrayIndexing-Parser extension.

    [author:]

        Claus Gittinger (cg@sinir)

    [instance variables:]

    [class variables:]

    [see also:]

        MultiDimensionalArrayAccessor

"

! !

!Matrix3_3 class methodsFor:'instance creation'!

new

    ^ self basicNew:3*3

! !

!Matrix3_3 methodsFor:'accessing'!

_at:index1 at:index2

    "this is a synthetic selector, generated by the compiler,

     if a construct of the form expr[idx...] is parsed.

     I.e. 

        foo[n,m]

     generates

        foo _at:n at:m

    "

    |idx|

    (index1 between:1 and:3) ifFalse:[self subscriptBoundsError:index1].

    (index2 between:1 and:3) ifFalse:[self subscriptBoundsError:index2].

    idx := index1 * 3 - 3 + index2.

    ^ self basicAt:idx.

!

_at:index1 at:index2 put:value

    "this is a synthetic selector, generated by the compiler,

     if a construct of the form expr[idx...] := val is parsed.

     I.e. 

        foo[n,m] := val

     generates

        foo _at:n at:m put:val

    "

    |idx|

    (index1 between:1 and:3) ifFalse:[self subscriptBoundsError:index1].

    (index2 between:1 and:3) ifFalse:[self subscriptBoundsError:index2].

    idx := index1 * 3 - 3 + index2.

    ^ self basicAt:idx put:value.

! !

!Matrix3_3 methodsFor:'matrix operations'!

determinantByCofactors

    "Answer the determinant of this matrix."

    ^ ((self _at: 1 at: 1) * (((self _at: 2 at: 2)*(self _at: 3 at: 3)) - ((self _at: 3 at: 2)*(self _at: 2 at: 3)))) -

      ((self _at: 1 at: 2) * (((self _at: 2 at: 1)*(self _at: 3 at: 3)) - ((self _at: 3 at: 1)*(self _at: 2 at: 3)))) +

      ((self _at: 1 at: 3) * (((self _at: 2 at: 1)*(self _at: 3 at: 2)) - ((self _at: 3 at: 1)*(self _at: 2 at: 2)))).

! !

!Matrix3_3 class methodsFor:'documentation'!

version_CVS

    ^ '$Header$'

! !