addStructs

Adds the numeric values in two structures.

S = addStructs(S1, S2)

Given two structs S1 and S2, returns a struct S such that
S.<fieldName> = S1.<fieldName> + S2.<fieldName> for all
fieldNames whose corresponding values are both numeric
and the same length in both S1 and S2.

If the values are not numeric or not the same length, the
value from S1 is copied to S.

This function will throw an error if the field names in
S1 and S2 are not the same.

Example:

>> s1

s1 =

a: 1
b: 2
c: [1 2 3]
foo: 'bar'

>> s2

s2 =

a: 1
b: 4
c: 3
foo: 'baz'

>> addStructs(s1, s2)

ans =

a: 2
b: 6
c: [1 2 3]
foo: 'bar'