The reader of appels inspirational book 1 may be thinking just use continuationpassing style cps. The formal relationship between direct and continuation. Mar 31, 2020 scheduler bypass is an optimization where you directly specify the next task to run. 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. Jun 16, 2019 both compilers use the strategy of converting the source program to continuation page 20 10 passing style. It begins by presenting a simple transformation of callbyneed. We separate the code generation into phases that rewrite this representation into eversimpler forms. It translates slightly flavored javascript syntax into standard javascript, so it can be also called a translator. Denotational style correctness of a cpstransform based compiler. It also means that most but not quite all code that can be compiled by clojure. 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. Continuation passing style cps for short is a style of programming in which functions do not return values. Continuation passing style has been used as an intermediate language in a number of compilers for functional languages 1, 8, 12. Continuationpassing style in javascript matt might.
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. This paper describes the implementation of a small experimental scheme compiler, using continuation passing style cps as an intermediate representation for the source code. 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. Were going to rewrite our evaluator in continuationpassing style cps. Well solve the first problem here, unfortunately at the cost of making it even slower.
Tailrecursive, continuationpassing style the scala. We present a parallel version of continuation passing style, called pcps. Obviously, cps quickly fills the stack or has to be given handcoded. If youre new to continuationpassing style, i recommend my earlier post on. Citeseerx continuation passing style in c and the cost. This, in combination with a solid theoretical basis lambda. Keywords continuations, continuation passing style, monads, optimizing compilation, functional programming languages 1. Contribute to kerneiscpc development by creating an account on github. Continuation passing style in c and the cost of tailcall elimination with gcc. Haskellcontinuation passing style wikibooks, open books. Citeseerx continuationpassingstyle as an intermediate. Continuationpassing style cps is a good abstract representation to use for compilation and optimization.
Our cps language is represented as an ml datatype in which all functions are named and most kinds of illformed expressions are impossible. In functional programming, continuationpassing style cps is a style of programming in which. Continuationpassing style, or cps more shortly, is a style of programming. Some code generators can cleverly eliminate the closures, but perhaps not if further transformations intervene. It will be essential reading for compiler writers in both industry and academe, as well as for students and researchers in programming language theory.
Cs 6110 lecture continuationpassing style 20 february. 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. Recently it has been discovered that cps resolves a longstanding structural problem in the composition of software reliability. If this feature is generalised to an inline compiler then there might be a glimmer of hope. A correspondence between continuation passing style and static single assignment form.
A tractable proof for this compiler is presented, including a denotational proof of the correctness of a cpstransform. In the context of functional languages, there has been an extensive debate on the advantages and disadvantages of continuation passing style cps. So report the authors of two classic papers on continuationpassing style in recent retrospectives. Programming languages and compilers cs 421 william. Our central result is a precise correspondence between the two compilation strategies. Compiling with continuations books pics download new. 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.
In continuation passing style, callcc becomes a simple function that can be written with lambda. Continuation passing style has been used as a programming style as well as a compilation technique in functional programming languages for over 20 years. 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. Im interested in programming and programming languages. Citeseerx parallel continuationpassing style a compiler. 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.
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. Continuationpassing, closurepassing style proceedings of. 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. The first compiler known as cheapy was written as a throwaway implementation to test the concept of conversion to continuation passing style. Pdf continuationpassingstyle has been used as a programming style as. We explain how cps works and give tips for using it. Static single assignment form has been used in optimizations targeted towards imperative languages, for exam ple eliminating induction variables and par tim redundancies 2. 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. The pattern is useful for tail call optimization because it allows computations to be passed along for somebody else to do. The cpc compiler uses a compilation technique, based on the cps transform, that yields efficient code and an extremely. The cpc compiler uses a compilation technique, based on the cps transform, that yields efficient code and an extremely lightweight representation for contexts. For example, at the end of the continuation passing example in the previous section, method execute spawns task a and returns. In proceedings of the third acm sigplan workshop on continuations cw01, pages 22, january 2001. Your task is to experiment with continuation passing style and to write at least one function, anything you like, in continuation passing style.
Consider the procedurecall mechanisms used by conventional compilers. In the authors opinion, this approach gives the best of the two worlds. Callbyneed and continuationpassing style springerlink. A correspondence between continuation passing style and.
C using a technique known as conversion into continuation passing style. Asynchronous programming and continuationpassing style in. Here normal clojure code, means code that is not written in cps. Calleesave registers in continuationpassing style springerlink.
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. Find out information about continuation passing style. This book shows how continuation passing style is used as an intermediate representation on which to perform optimisations and program transformations. Introduction compiling with continuations is out of fashion. 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. This paper examines the transformation of callbyneed. Pdf continuation passing style in c and the cost of tailcall. Continuation passing style cps is a method of programming which allows for intricate manipulation of control flow while still maintaining functional purity. Continuations can be used to compile most programming languages. The concept of continuation passing style, or cps wikipedia has more info, however, seems to have a lot more to offer. Continuationpassing style cps originated as a style of programming in the 1970s, and it rose to prominence as an intermediate representation for compilers of.
The method is illustrated in a compiler for the programming language standard ml. Continuation passing s tyle in c and the cost of t ail call elimination with gcc. From this, an informal derivation is carried out, resulting in a translation from. Here a simple source language and its cpstransform based compiler are introduced. Pdf continuation passing style in c and the cost of tail. 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. Cs 6110 lecture continuationpassing style 20 february 20 lecturer. Citeseerx document details isaac councill, lee giles, pradeep teregowda. A semantically clean language with continuations used as an intermediate language for scheme and the smlnj compiler. Continuation passing style often opens up an opportunity for scheduler bypass. You can try to use the term continuation monad to find some additional articles.
Cps is a form of code that makes control flow and control information explicit. Continuation passing style article about continuation. The consensus seems to be that some form of explicit continuations is necessary. However, in practice, the continuation passing style cps transform or a variant is often used in the translation process. We implemented a continuation passing style cps code generator for ml. In this blog post, we give a name to javascripts callbackbased asynchronous programming style. In 2002, then, cps would appear to be a lesson aban. Then, during cps transformation, continuations desugar into functions. Reasoning about programs in continuationpassing style. A compiler for javascript asynchronous continuationpassing style transformation programleaguejscps. This book shows how continuation passing style is used as an intermediate representation to perform optimizations and program transformations. Cps is used more frequently by compilers than by programmers as a local or global style. To compile a cpc program, use the wrapper in bincpc for.
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