Clippings

There are two basic styles for expressing functions, the pointwise style and the point-free style. In the pointwise style we describe a function by describing its application to arguments. … In the point-free style we describe a function exclusively in terms of functional composition. …we want to illustrate … how a point-free style leads to a very simple method for reasoning about functions.

One does not so much learn category theory as absorb it over a period of time. It is difficult, at a first or second reading, to appreciate the point of many definitions and the reasons for the subject’s abstract nature.