I figured this answer had been asked before, so I searched, but I couldn't find anything. Granted, there are a ton of Ruby Array questions, so it might be there, just buried. In any case, I'm trying to reduce a cross-product of ranges, returning a sum of all elements of the cross-product that meet some set of conditions. To construct a trivial example, if I have an array like this: [0..1,0..1,0..1] I'd like to iterate over this set: [ [0,0,0], [0,0,1], [0,1,0], [0,1,1], [1,0,0], [1,0,1], [1,1,0], [1,1,1] ] and return a sum based the condition "return 1 if i[0] == 1 and i[2] == 0" (which would give 2). In my contrived example, I could do it like this: br = 0..1 br.reduce(0){|sumx, x| sumx + br.reduce(0){|sumy, y| sumy + br.reduce(0){|sumz, z| sumz + (x == 1 and z == 0 ? 1 : 0) } } } , but in the actual application, the set of ranges might be much larger, and nesting reduces that way would get quite ugly. Is there a better way?