Lists are often used as "glue" to connect separate parts of a program together. We propose an automatic technique for improving the efficiency of such programs, by removing many of these intermediate lists, based on a single, simple, local transformation. We have implemented the method in the Glasgow Haskell compiler.

This is the final report on the GRASP project, carried out under SERC grants GR/F34671 and GR/F98444, at Glasgow University 1 2 . The project supported two Principal Investigators (Simon Peyton Jones and Phil Wadler), and three Research Assistants (Kevin Hammond, Cordelia Hall and Will Partain). Four research students have worked in close association with the project. 1 Summary The purpose of GRASP was to help get the technology of functional programming out of the lab and into the hands of practitioners, by producing robust and usable compilers and profilers for these languages, on both sequential and parallel systems. The main achievements of the project are as follows: ffl We have played a key role in the development of a common international non-strict functional language, Haskell (Hudak et al. [1992]). This standardisation effort has led directly to a considerable focussing of the international research community in these languages. More details about Haskell are given in Sect...

Some algorithms make critical internal use of updatable state, even though their external specification is purely functional. Based on earlier work on monads, we present a way of securely encapsulating stateful computations that manipulate multiple, named, mutable objects, in the context of a non-strict, purely-functional language. The security of the encapsulation is assured by the type system, using parametricity. The same framework is also used to handle input/output operations (state changes on the external world) and calls to C.