We study the representation of additive functors over the functor category Mod C,convert an Abel group into a left C-module in Mod C,construct a Hom functor and a functorial morphism, and prove that any contravariant left exact additive functor F:Mod C→Ab converting sums to products is equivalent to some Hom functor.
研究函子范畴ModC上加性函子的表示,把一个Abel群作成范畴ModC上的一个左C-模,构造出一个Hom函子和一个函子态射,证明了从函子范畴ModC到范畴Ab的任意变和为积的反变左正合可加函子都与某个Hom函子自然等价。