Matrix multiplication: Difference between revisions

=={{header|FreeBASIC}}==

<lang freebasic>type Matrix

dim as double m( any , any )

declare constructor ( )

declare constructor ( byval x as uinteger , byval y as uinteger )

end type

constructor Matrix ( )

end constructor

constructor Matrix ( byval x as uinteger , byval y as uinteger )

redim this.m( x - 1 , y - 1 )

end constructor

operator * ( byref a as Matrix , byref b as Matrix ) as Matrix

dim as Matrix ret

dim as uinteger i, j, k

if ubound( a.m , 2 ) = ubound( b.m , 1 ) and ubound( a.m , 1 ) = ubound( b.m , 2 ) then

redim ret.m( ubound( a.m , 1 ) , ubound( b.m , 2 ) )

for i = 0 to ubound( a.m , 1 )

for j = 0 to ubound( b.m , 2 )

for k = 0 to ubound( b.m , 1 )

ret.m( i , j ) += a.m( i , k ) * b.m( k , j )

next k

next j

next i

end if

return ret

end operator

'some garbage matrices for demonstration

dim as Matrix a = Matrix(4 , 2)

a.m(0 , 0) = 1 : a.m(0 , 1) = 0

a.m(1 , 0) = 0 : a.m(1 , 1) = 1

a.m(2 , 0) = 2 : a.m(2 , 1) = 3

a.m(3 , 0) = 0.75 : a.m(3 , 1) = -0.5

dim as Matrix b = Matrix( 2 , 4 )

b.m(0 , 0) = 3.1 : b.m(0 , 1) = 1.6 : b.m(0 , 2) = -99 : b.m (0, 3) = -8

b.m(1 , 0) = 2.7 : b.m(1 , 1) = 0.6 : b.m(1 , 2) = 0 : b.m(1,3) = 21

dim as Matrix c = a * b

print c.m(0, 0), c.m(0, 1), c.m(0, 2), c.m(0, 3)

print c.m(1, 0), c.m(1, 1), c.m(1, 2), c.m(1, 3)

print c.m(2, 0), c.m(2, 1), c.m(2, 2), c.m(2, 3)

print c.m(3, 0), c.m(3, 1), c.m(3, 2), c.m(3, 3)

</lang>