Bird–Meertens formalism

The Bird–Meertens formalism (BMF) is a calculus for deriving programs from program specifications (in a functional programming setting) by a process of equational reasoning. It was devised by Richard Bird and Lambert Meertens as part of their work within IFIP Working Group 2.1.

It is sometimes referred to in publications as BMF, as a nod to Backus–Naur form. Facetiously it is also referred to as Squiggol, as a nod to ALGOL, which was also in the remit of WG 2.1, and because of the "squiggly" symbols it uses. A less-used variant name, but actually the first one suggested, is SQUIGOL. Martin and Nipkow provided automated support for Squiggol development proofs, using the Larch Prover.