#	product() gives product
#	e.g product(x-j, j,1,3,1) gives (x-1) (x-2) (x-3)
#	See also: sum.;

product(y_,x_,a_,b_,c_) := block(prod:=1,
	For(x_,a_,b_,c_,prod:=prod*y_),
	prod);
product(y_,x_,a_,b_) := prod(y_, x_,a_,b_,1);
product(y_,x_) := prod(y_, x_,1,5,1);
product(y_) := prod(y_, x,1,5,1);