# An Introduction to the Bird−Meertens Formalism

Jeremy Gibbons

### Abstract

The Bird-Meertens Formalism, or Squiggol', is a calculus for the construction of programs from their specifications by a process of equational reasoning. Developments are directed by considerations of \em data, as opposed to \em program, structure. \par This paper presents a brief introduction to the philosophy and notation of the calculus, in the guise of the (well-known) derivation of a linear-time solution to the maximum segment sum' problem.