Efficient colon operator for multiple start and end points

Question

Suppose I have the following two variables:

start_idx = [1 4 7];
end_idx   = [2 6 15];

I want to efficiently (no for loop

Answer 1

This is cumbersome, but perhaps faster:

x = min(start_idx):max(end_idx);
m = sum(bsxfun(@ge,x,start_idx(:)),1)==numel(end_idx)-sum(bsxfun(@le,x,end_idx(:)),1)+1;
result = x(m);

It correctly handles empty ranges, i.e.

start_idx = [1 4 16]
end_idx   = [2 6 15];

gives

result =
     1     2     4     5     6