Packs information from each element of two vectors into the result vector.
Elemental function
If ARG1 is an INTEGER(2) vector, then the result is an INTEGER(1) vector. If ARG1 is an INTEGER(4) vector, then the result is an INTEGER(2) vector. If ARG1 is an UNSIGNED(2) vector, then the result is an UNSIGNED(1) vector. If ARG1 is an UNSIGNED(4) vector, then the result is an UNSIGNED(2) vector.
The value of each element of the result vector is taken from the low-order half of the corresponding element of the result of concatenating ARG1 and ARG2.