#proc det matrix {
def det(matrix):
	#if {[llength $matrix] != [llength [lindex $matrix 0]]} {
	if matrix.len()[0] != matrix.len()[1]:
		#error "non-square matrix"
		raise SizeError, "non-square matrix"
	#}
	#switch [llength $matrix] {
	#   2 {
	if matrix.len()[0] == 2:
		#foreach {a b c d} [join $matrix] break
		a,b,c,d = matrix[0,0], matrix[0,1], matrix[1,0], matrix[1,1]
		#expr {$a*$d - $b*$c}
		return a*d - b*c
	#   } default {
	else:
		#set i 0
		i = 0
		#set mat2 [lrange $matrix 1 end]
		mat2 = matrix[1:,...]
		#set res 0
		res = 0
		#foreach element [lindex $matrix 0] {
		for element in matrix[0]
			#if $element {
			if element:
				#set sign [expr {$i%2? -1: 1}]
				if i%2: sign = -1
				else: sign = 1
				#set res [expr {$res + $sign*$element* [det [cancelcol $i $mat2]]}]
				res += sign * element * det(cancelcol(i, mat2))
			#}
			#incr i
			i += 1
		#}
		#set res
		return res
	#  }
	#}
#}

#proc cancelcol {n matrix} {
def cancelcol(n, matrix)
	#set res {}
	res = []
	#foreach row $matrix {
	for row in matrix.rows:
		#lappend res [lreplace $row $n $n]
		res += [row[n]]
	#}
	#set res
	return res
#}