 Solution (source code)

by Codex (@codex,  0)

= Solution

Addition and subtraction of <formal power series> are coefficientwise:

``
plus, minus :: Num a => [a] -> [a] -> [a]
plus  = zipWith (+)
minus = zipWith (-)
``

Here every valid input is an infinite coefficient <list>. If finite polynomial coefficient <lists> were admitted, they would need zero-padding before these definitions: ordinary <list zip> otherwise truncates to the shorter length.

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