In this chapter, we are going to consider how that plays out in haskell and, in particular, how cps can be expressed with a monad. Obviously, cps quickly fills the stack or has to be given handcoded. Cps is used more frequently by compilers than by programmers as a local or global style. In functional programming, continuationpassing style cps is a style of programming in which. You can try to use the term continuation monad to find some additional articles. For example, at the end of the continuation passing example in the previous section, method execute spawns task a and returns. It also means that most but not quite all code that can be compiled by clojure.
If this feature is generalised to an inline compiler then there might be a glimmer of hope. Mar 31, 2020 scheduler bypass is an optimization where you directly specify the next task to run. A compiler for javascript asynchronous continuationpassing style transformation programleaguejscps. Well solve the first problem here, unfortunately at the cost of making it even slower. Find out information about continuation passing style.
Consider the procedurecall mechanisms used by conventional compilers. Continuationpassing style, or cps more shortly, is a style of programming. Continuation passing s tyle in c and the cost of t ail call elimination with gcc. This is a particularly common strategy in haskell, where it is easy to construct a continuation passing monad for example, the cont monad and contt monad transformer in the mtl library.
Recently it has been discovered that cps resolves a longstanding structural problem in the composition of software reliability. Using pcps as the intermediate representation allows a compiler to first translate a sequential program into a form with explicit scheduling and then gradually increase the parallelism by removing happensbefore constraints whenever possible. Then, during cps transformation, continuations desugar into functions. Denotational style correctness of a cpstransform based compiler. Your task is to experiment with continuation passing style and to write at least one function, anything you like, in continuation passing style. The pattern is useful for tail call optimization because it allows computations to be passed along for somebody else to do. Citeseerx continuationpassingstyle as an intermediate. Pdf continuation passing style in c and the cost of tail. Citeseerx continuation passing style in c and the cost. The cpc compiler uses a compilation technique, based on the cps transform, that yields efficient code and an extremely. This, in combination with a solid theoretical basis lambda.
Continuationpassing style in javascript matt might. Compiling with continuations books pics download new. A semantically clean language with continuations used as an intermediate language for scheme and the smlnj compiler. Pdf continuationpassingstyle has been used as a programming style as. Citeseerx document details isaac councill, lee giles, pradeep teregowda. The concept of continuation passing style, or cps wikipedia has more info, however, seems to have a lot more to offer. Chicken scheme compiler, a scheme to c compiler that uses continuationpassing style for translating scheme procedures into c functions while using the cstack as the nursery for the generational garbage collector. Cs 6110 lecture continuationpassing style 20 february 20 lecturer. Introduction compiling with continuations is out of fashion. Some code generators can cleverly eliminate the closures, but perhaps not if further transformations intervene. The semantics of cpc is defined as a sourcetosource translation from cpc into plain c using a technique known as conversion into continuation passing style.
Programming languages and compilers cs 421 william. We separate the code generation into phases that rewrite this representation into eversimpler forms. Continuation passing style article about continuation. Our cps language is represented as an ml datatype in which all functions are named and most kinds of illformed expressions are impossible. In the authors opinion, this approach gives the best of the two worlds. However, in practice, the continuation passing style cps transform or a variant is often used in the translation process.
In continuation passing style, callcc becomes a simple function that can be written with lambda. Continuation passing style has been used as an intermediate language in a number of compilers for functional languages 1, 8, 12. Reasoning about programs in continuationpassing style. Jun 16, 2019 both compilers use the strategy of converting the source program to continuation page 20 10 passing style. In this blog post, we give a name to javascripts callbackbased asynchronous programming style. Apr 03, 2018 and compilers are able to aggressively optimize programs written in continuation passing style because everything the compiler needs to know about a function is available in the continuation. A correspondence between continuation passing style and static single assignment form. It provides a sourcetosource compiler for transforming normal clojure code to clojure code in continuation passing style cps, as well as runtime support for executing the transformed code. It translates slightly flavored javascript syntax into standard javascript, so it can be also called a translator. Contribute to kerneiscpc development by creating an account on github. Compilers for higherorder programming languages like scheme, ml, and lisp can be broadly characterized as either direct compilers or continuation passing style cps compilers, depending on their main intermediate representation. The cpc compiler uses a compilation technique, based on the cps transform, that yields efficient code and an extremely lightweight representation for contexts.
So report the authors of two classic papers on continuationpassing style in recent retrospectives. Calleesave registers in continuationpassing style springerlink. This book shows how continuation passing style is used as an intermediate representation to perform optimizations and program transformations. This paper describes the implementation of a small experimental scheme compiler, using continuation passing style cps as an intermediate representation for the source code. We implemented a continuation passing style cps code generator for ml. In this paper, we introduce continuation passing c cpc, a programming language for concurrent systems in which native and cooperative threads are unified and presented to the programmer as a single abstraction.
C using a technique known as conversion into continuation passing style. Our central result is a precise correspondence between the two compilation strategies. Asynchronous programming and continuationpassing style in. We present a parallel version of continuation passing style, called pcps. Continuations can be used to compile most programming languages. The consensus seems to be that some form of explicit continuations is necessary. Haskellcontinuation passing style wikibooks, open books. Here a simple source language and its cpstransform based compiler are introduced. We explain how cps works and give tips for using it. From this, an informal derivation is carried out, resulting in a translation from. It begins by presenting a simple transformation of callbyneed.
A tractable proof for this compiler is presented, including a denotational proof of the correctness of a cpstransform. Static single assignment form has been used in optimizations targeted towards imperative languages, for exam ple eliminating induction variables and par tim redundancies 2. Continuationpassing style cps is a good abstract representation to use for compilation and optimization. This book shows how continuation passing style is used as an intermediate representation on which to perform optimisations and program transformations. Continuation passing style has been used as a programming style as well as a compilation technique in functional programming languages for over 20 years.
Im interested in programming and programming languages. Chicken scheme compiler, a scheme to c compiler that uses continuation passing style for translating scheme procedures into c functions while using the cstack as the nursery for the generational garbage collector. Continuationpassing, closurepassing style proceedings of. In computer science, anormal form abbreviated anf is an intermediate representation of programs in functional compilers introduced by sabry and felleisen in 1992 as a simpler alternative to continuation passing style cps. Continuation passing style often opens up an opportunity for scheduler bypass. This paper examines the transformation of callbyneed.
Nov 19, 20 lets take a break from type classes and take a brief look at one of the more esoteric concepts of functional programming. Keywords continuations, continuation passing style, monads, optimizing compilation, functional programming languages 1. Continuation passing style cps for short is a style of programming in which functions do not return values. Cps is a form of code that makes control flow and control information explicit. Continuation passing style cps is a method of programming which allows for intricate manipulation of control flow while still maintaining functional purity. Pdf continuation passing style in c and the cost of tailcall. A correspondence between continuation passing style and.
Cs 6110 lecture continuationpassing style 20 february. Here normal clojure code, means code that is not written in cps. In the context of functional languages, there has been an extensive debate on the advantages and disadvantages of continuation passing style cps. The formal relationship between direct and continuation. Andrew myers continuationpassing style cps cps semantics cps conversion 1 the limitations of direct translation so far we have been building translations that preserve control. In proceedings of the third acm sigplan workshop on continuations cw01, pages 22, january 2001. Callbyneed and continuationpassing style springerlink. Continuation passing style in c and the cost of tailcall elimination with gcc. Tailrecursive, continuationpassing style the scala. It will be essential reading for compiler writers in both industry and academe, as well as for students and researchers in programming language theory. Throughout the course, students will design and implement a substantial functionallanguage compiler of their own, over the course of several projects, and will explore various compiler related topics such as intermediate representations, desugaring, continuation passing style, closure conversion, formal semantics, garbage collection, type. In 2002, then, cps would appear to be a lesson aban.
1526 1221 1235 914 1525 1062 1555 828 320 228 994 67 1172 1600 325 601 488 454 593 1095 1194 956 1061 1607 1238 458 981 1638 58 1027 1064 1012 1140 613 716 1364 403