Matrix multiplication: Difference between revisions

<lang rexx>/*REXX program multiplies two matrices together, displays the matrices and resultthe results. */

x.=; x.1=1 2 /*╔═══════════════════════════════════╗*/

x.2=3 4 /*║ As none of the matrix values have ║*/

x.3=5 6 /*║ a sign, quotes aren't needed. ║*/

x.4=7 8 /*╚═══════════════════════════════════╝*/

do r=1 while x.r\=='' /*build the "A" matrix from X. numbers.*/

do c=1 while x.r\==''; parse var x.r a.r.c x.r; end /*c*/

end /*r*/

Arows=r-1 /*adjust the number of rows (DO loop).*/

Acols=c-1 /* " " " " cols " " .*/

y.=; y.1=1 2 3

y.2=4 5 6

do r=1 while y.r\=='' /*build the "B" matrix from Y. numbers.*/

do c=1 while y.r\==''; parse var y.r b.r.c y.r; end /*c*/

end /*r*/

Brows=r-1 /*adjust the number of rows (DO loop).*/

Bcols=c-1 /* " " " " cols " " */

c.=0; w=0 /*W is max width of an matrix element.*/

do i=1 for Arows /*multiply matrix A and B ───► C */

do j=1 for Bcols

do k=1 for Acols; c.i.j=c.i.j + a.i.k * b.k.j

c.i.j = c.i.j + a.i.k * b.k.j; w=max(w, length(c.i.j))

end /*k*/ /* ↑ */

end /*j*/ /* └──◄─── maximum width of elements. */

end /*i*/

call showMatrix 'A', Arows, Acols /*display matrix A ───► the terminal.*/

call showMatrix 'B', Brows, Bcols /* " " B ───► " " */

call showMatrix 'C', Arows, Bcols /* " " C ───► " " */

exit /*stick a fork in it, we're all done. */

showMatrix: parse arg mat,rows,cols; say; say center(mat 'matrix', cols*(w+1) +4, say"─")

do r do c=1 for rowscols; _=_ right(value(mat'.'r"."c), w); end; say _

do c=1 for cols; _=_ right(value(mat'.'r'.'c), w); end; say _/*r*/

end return</*r*/lang>