Concurrent clean

Abstract

Concurrent Clean is an experimental, lazy, higher-order parallel functional p r ogramming language based on term graph rewriting. An important d i e r ence with other languages is that in Clean graphs are manipulated and not terms. This can beused by the programmer to control communication and sharing of computation. Cyclic structures can be de ned. Concurrent Clean furthermore a llows to control the (parallel) order of evaluation t o m a k e e cient e v aluation p o ssible. With help of sequential annotations the default lazy evaluation can be locally changed into eager evaluation. The language enables the de nition o f p a rtially strict data structures which m a ke a whole new class of a l g orithms feasible in a functional language. A p o werful and fast strictness analyser is incorporated in the system. The quality of the code generated b y the Clean compiler has been greatly improved such t h a t it is one of t h e b e st code generators f o r a l a zy functional language. Two v ery p o werful parallel annotations enable the programmer to de ne concurrent functional progra m s w i t h a rbitrary process topologies. Concurrent C l e a n i s s e t u p i n s u c h a way t h a t the e ciency achieved for the sequential c a se can largely be maintained for a p a rallel implementation on l o o sely coupled parallel machine architectures.

Trends in Trends in Functional Programming 1999/2000 versus 2007/2008

“…In 1999, the inception year for TFP, the trend to parallelize the code of programs written in a functional language was strong as evidenced by Alex Aiken's invited talk at ICFP 1999 on languages for parallel computing [4]. The successful development and implementation of parallel extensions of Lisp (e.g., MULTILISP [49]), Clean (Concurrent Clean [94]), and Haskell (Glasgow Parallel Haskell (GpH) [121]) established a new trend to parallelize sequential implementations of functional languages. Among the efforts to parallelize Haskell is Eden [79].…”

Safety of Nöcker's strictness analysis

“…This includes a case analysis, which can be modeled by unions or by nondeterministic choices, together with subsumption rules based on ⊥ 6 t 6 . This analysis was implemented at least twice: once by Nöcker in C for Concurrent Clean (Nöcker et al 1991) and once by Schütz in Haskell (Schütz 1994). As of Concurrent Clean version 2.1 Nöcker's C-implementation is still in use in the compiler.…”

The ins and outs of Clean I/O

“…Clean (Brus et al, 1987;Nocker et al, 1991;Plasmeijer and van Eekelen, 1993) is a lazy functional programming language based on Term Graph Rewriting (Barendregt et al, 1987). To give an idea of what Clean programs look like, Fig.…”