  Previous computation models either have equivalent abilities in representing
all computations but fail to provide primitive operators for programming
complex algorithms or lack generalized expression ability to represent
newly-added computations. This article presents a unified computation model
with generalized expression ability and a concise set of primitive operators
for programming high-level algorithms. We propose a unified data abstraction --
Tensor of List, and offer a unified computation model based on Tensor of List,
which we call the ToL model (in short, ToL). ToL introduces five atomic
computations that can represent any elementary computation by finite
composition, ensured with strict formal proof. Based on ToL, we design a
pure-functional language -- ToLang. ToLang provides a concise set of primitive
operators that can be used to program complex big data and AI algorithms. Our
evaluations show ToL has generalized expression ability and a built-in
performance indicator, born with a strictly defined computation metric --
elementary operation count (EOPs), consistent with FLOPs within a small error
range.
