SassyMatrix

All you ever wanted to deal with matrices in Sass.

What's in there?

matrix($x, $y: $x): create a matrix of $x rows by $y columns filled with 0s
unit-matrix($x, $y): create a matrix of $x rows by $y columns filled with 0s except the diagonal which is filled with 1s

set-entry($matrix, $coords, $value): set $value at $matrix[$coords[1], $coords[2]]
set-column($matrix, $index, $column: ()): set $column at $index in $matrix
set-row($matrix, $index, $row: ()): set $row at $index in $matrix
add-column($matrix, $column: (), $index: null): add $column at $index in $matrix
add-row($matrix, $row: (), $index: null): add $row at $index in $matrix

swap-entries($matrix, $e1, $e2): swaps values $e1 and $e2 from $matrix
swap-rows($matrix, $r1, $r2): swaps rows $r1 and $r2 from $matrix
swap-columns($matrix, $c1, $c2): swaps columns $c1 and $c2 from $matrix
transpose($matrix): rotates $matrix around its diagonal
add-matrices($matrix1, $matrix2): add $matrix1 and $matrix2

columns($matrix): return number of columns in $matrix
rows($matrix): return number of rows in $matrix
is-numeric($matrix): check whether $matrix has only numeric values
is-square($matrix): check whether $matrix has as many rows as columns
is-diagonal($matrix): check whether all values from the main diagonal of $matrix are set while all other values are equal to 0
is-lower-triangular($matrix, $flag: null): check whether all value below $matrix diagonal are equal to 0
is-upper-triangular($matrix, $flag: null): check whether all value above $matrix diagonal are equal to 0

All you need is a clean version of Sass 3.3. Otherwise it's just pure Sass madness.