# Computer science

*Computer Science is no more about computers than astronomy is about telescopes*.

-- E. W. Dijkstra

## Introduction

Wikipedia's Computer science.

Martín Escardó maintains a Computer science page, being both detailed and comprehensive. The Dijkstra-quotation cited above comes from this page.

Structure and Interpretation of Computer Programs (by Harold Abelson and Gerald Jay Sussman with Julie Sussman, foreword by Alan J. Perlis).

## Computability theory

Wikipedia's Computability theory.

An interesting area related to computabilty theory: Exact real arithmetic. For me, it was surprising, how it connected problems in mathematical analysis, arithmetic and computability theory.

## To do

There are several (equivalent) definitions to the concept of *algorithm*:

These can be conceived also as computer programming languages -- there should be implemented as many of them as possible. And some of them can be very good for making such jokes as

- self replication programs or self-representing formulas
- metacircular interpreters.

At least

- to write a combinatory logic expression which is equivalent to its own quotation (term representation)
- to specify and implement a programming language, which could be seen as an experimentable, playable incarnation of recursive function theory -- it could yield a playground for learning concepts like iteration theorem, recursion theorem, fixed point theorem

Although there are many differences between Combinatory logic and recursive function theory, I suspect they have some important common features

- both of them allow us to avoid the concept of variable
- both of them can be used well for metaprogramming

Algorithmic information theory may exemplify relatedness of computer science to philosophical and foundational questions of mathematics.