ruby narray concatenation

Question

Given say 2x3 and mx3 arrays (I have used NArray): how to construct a (2+m)x3 array, the concatenation of each. + or << do not keep the elements properly aligned. e.g.

a = [[1,2,3],[4,5,6]]
b = [[1,2,3,4],[5,6,7,8]]
# should be concatenated as:
# [[1,2,3,1,2,3,4],[4,5,6,5,6,7,8]]

Thanks.

Answer 1

Cary,

I have a loop which grows an array, each addition length is undetermined. I begin with an array and concatenate. One dimension is fixed, say 2. I am therefore looking for a way to grow the initial, say 2x3 array through concatenation to a 2x7, ... A becomes [A C], which becomes [A C D] ...

Thanks.

Answer 2

You can do it this way:

a = [[1,2,3],[4,5,6]]
b = [[1,2,3,4],[5,6,7,8]]
a.zip(b).map{|x, y| x+y}
# => [[1,2,3,1,2,3,4],[4,5,6,5,6,7,8]]