change array dimension

Hello,

is it possible to change the dimension of an array? I am looking for something
like this:

SELECT change_array_dims('[1:2][1:2]', '{1,2,3,4}'::int[]);
 change_array_dims
-------------------
 {{1,2},{3,4}}

and the other way around:

SELECT change_array_dims('[1:4]', '{{1,2},{3,4}}'::int[]);
 change_array_dims
-------------------
 {1,2,3,4}

Does such a function exist?

Thanks,
  Gerhard