Question: How can I obtain this result?

Is there a simpler and more elegant way to get the last result in this code snippet?

add(f~([op(a+b)])[]);
                          f(a) + f(b)
# simpler and more elegant
map(f, a+b);
                          f(a) + f(b)
# now I want to obtain this result
add(f~([op(a+b)], t)[]);
                       f(a, t) + f(b, t) 

TIA

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