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Multi-Return Function Call
To appear in J. Functional Programming 1 Multi-return Function Call OLIN SHIVERS and DAVID FISHER College of Computing Georgia Institute of Technology (e-mail: fshivers,[email protected]) Abstract It is possible to extend the basic notion of “function call” to allow functions to have multiple re- turn points. This turns out to be a surprisingly useful mechanism. This article conducts a fairly wide-ranging tour of such a feature: a formal semantics for a minimal λ-calculus capturing the mechanism; motivating examples; monomorphic and parametrically polymorphic static type sys- tems; useful transformations; implementation concerns and experience with an implementation; and comparison to related mechanisms, such as exceptions, sum-types and explicit continuations. We conclude that multiple-return function call is not only a useful and expressive mechanism, at both the source-code and intermediate-representation levels, but also quite inexpensive to implement. Capsule Review Interesting new control-flow constructs don’t come along every day. Shivers and Fisher’s multi- return function call offers intriguing possibilities—but unlike delimited control operators or first- class continuations, it won’t make your head hurt or break the bank. It might even make you smile when you see the well-known tail call generalized to a “semi-tail call” and a “super-tail call.” What I enjoyed the most was the chance to reimagine several of my favorite little hacks using the new mechanism, but this unusually broad paper offers something for everyone: the language designer, the theorist, the implementor, and the programmer. 1 Introduction The purpose of this article is to explore in depth a particular programming-language mech- anism: the ability to specify multiple return points when calling a function. -
Aeroscript Programming Language Reference
AeroScript Programming Language Reference Table of Contents Table of Contents 2 Structure of a Program 5 Comments 6 Preprocessor 7 Text Replacement Macro (#define/#undef) 7 Source File Inclusion (#include) 8 Conditional Inclusion (#if/#ifdef/#ifndef) 8 Data Types and Variables 11 Fundamental Data Types 11 Fundamental Numeric Data Types 11 Fundamental String Data Type 11 Fundamental Axis Data Type 11 Fundamental Handle Data Type 12 Aggregate Data Types 12 Array Data Types 12 Structure Data Types 13 Enumerated Data Types 14 Variables 15 Variable Declaration 15 Variable Names 15 Numeric, Axis, and Handle Variable Declaration Syntax 15 String Variable Declaration Syntax 15 Syntax for Declaring Multiple Variables on the Same Line 16 Array Variable Declaration Syntax 16 Structure Variable Definition and Declaration Syntax 16 Definition Syntax 16 Declaration Syntax 17 Member Access Syntax 17 Enumeration Variable Definition and Declaration Syntax 18 Definition 18 Declaration Syntax 19 Enumerator Access Syntax 19 Variable Initialization Syntax 20 Basic Variable Initialization Syntax 20 Array Variable Initialization Syntax 21 Structure Variable Initialization Syntax 22 Enumeration Variable Initialization Syntax 22 Variable Scope 23 Controller Global Variables 23 User-Defined Variables 23 User-Defined Variable Accessibility 23 User-Defined Local Variable Declaration Location 25 Variable Data Type Conversions 26 Properties 27 Property Declaration 27 Property Names 27 Property Declaration 28 Property Usage 28 Expressions 29 Literals 29 Numeric Literals -
The Basics of Exception Handling
The Basics of Exception Handling MIPS uses two coprocessors: C0 and C1 for additional help. C0 primarily helps with exception handling, and C1 helps with floating point arithmetic. Each coprocessor has a few registers. Interrupts Initiated outside the instruction stream Arrive asynchronously (at no specific time), Example: o I/O device status change o I/O device error condition Traps Occur due to something in instruction stream. Examples: o Unaligned address error o Arithmetic overflow o System call MIPS coprocessor C0 has a cause register (Register 13) that contains a 4-bit code to identify the cause of an exception Cause register pending exception code interrupt Bits 15-10 Bits 5-2 [Exception Code = 0 means I/O interrupt = 12 means arithmetic overflow etc] MIPS instructions that cause overflow (or some other violation) lead to an exception, which sets the exception code. It then switches to the kernel mode (designated by a bit in the status register of C0, register 12) and transfers control to a predefined address to invoke a routine (exception handler) for handling the exception. Interrupt Enable Status register Interrupt Mask 15-8 1 0 Kernel/User (EPC = Exception Program Counter, Reg 14 of C0) Memory L: add $t0, $t1, $t2 overflow! Return address (L+4) Exception handler routine is saved in EPC Next instruction Overflow ra ! EPC; jr ra Invalid instruction ra ! EPC; jr ra System Call ra ! EPC; jr ra The Exception Handler determines the cause of the exception by looking at the exception code bits. Then it jumps to the appropriate exception handling routine. -
The Cool Reference Manual∗
The Cool Reference Manual∗ Contents 1 Introduction 3 2 Getting Started 3 3 Classes 4 3.1 Features . 4 3.2 Inheritance . 5 4 Types 6 4.1 SELF TYPE ........................................... 6 4.2 Type Checking . 7 5 Attributes 8 5.1 Void................................................ 8 6 Methods 8 7 Expressions 9 7.1 Constants . 9 7.2 Identifiers . 9 7.3 Assignment . 9 7.4 Dispatch . 10 7.5 Conditionals . 10 7.6 Loops . 11 7.7 Blocks . 11 7.8 Let . 11 7.9 Case . 12 7.10 New . 12 7.11 Isvoid . 12 7.12 Arithmetic and Comparison Operations . 13 ∗Copyright c 1995-2000 by Alex Aiken. All rights reserved. 1 8 Basic Classes 13 8.1 Object . 13 8.2 IO ................................................. 13 8.3 Int................................................. 14 8.4 String . 14 8.5 Bool . 14 9 Main Class 14 10 Lexical Structure 14 10.1 Integers, Identifiers, and Special Notation . 15 10.2 Strings . 15 10.3 Comments . 15 10.4 Keywords . 15 10.5 White Space . 15 11 Cool Syntax 17 11.1 Precedence . 17 12 Type Rules 17 12.1 Type Environments . 17 12.2 Type Checking Rules . 18 13 Operational Semantics 22 13.1 Environment and the Store . 22 13.2 Syntax for Cool Objects . 24 13.3 Class definitions . 24 13.4 Operational Rules . 25 14 Acknowledgements 30 2 1 Introduction This manual describes the programming language Cool: the Classroom Object-Oriented Language. Cool is a small language that can be implemented with reasonable effort in a one semester course. Still, Cool retains many of the features of modern programming languages including objects, static typing, and automatic memory management. -
C Programming Tutorial
C Programming Tutorial C PROGRAMMING TUTORIAL Simply Easy Learning by tutorialspoint.com tutorialspoint.com i COPYRIGHT & DISCLAIMER NOTICE All the content and graphics on this tutorial are the property of tutorialspoint.com. Any content from tutorialspoint.com or this tutorial may not be redistributed or reproduced in any way, shape, or form without the written permission of tutorialspoint.com. Failure to do so is a violation of copyright laws. This tutorial may contain inaccuracies or errors and tutorialspoint provides no guarantee regarding the accuracy of the site or its contents including this tutorial. If you discover that the tutorialspoint.com site or this tutorial content contains some errors, please contact us at [email protected] ii Table of Contents C Language Overview .............................................................. 1 Facts about C ............................................................................................... 1 Why to use C ? ............................................................................................. 2 C Programs .................................................................................................. 2 C Environment Setup ............................................................... 3 Text Editor ................................................................................................... 3 The C Compiler ............................................................................................ 3 Installation on Unix/Linux ............................................................................ -
Functions in C
Functions in C Fortran 90 has three kinds of units: a program unit, subroutine units and function units. In C, all units are functions. For example, the C counterpart to the Fortran 90 program unit is the function named main: #include <stdio.h> main () /* main */ f float w, x, y, z; int i, j, k; w = 0.5; x = 5.0; y = 10.0; z = x + y * w; i = j = k = 5; printf("x = %f, y = %f, z = %f n", x, y, z); printf("i = %d, j = %d, k = %dnn", i, j, k); /* main */ n g Every C program must have a function named main; it’s the func- tion where the program begins execution. C also has a bunch of standard library functions, which are functions that come predefined for everyone to use. 1 Standard Library Functions in C1 C has a bunch of standard library functions that everyone gets to use for free. They are analogous to Fortran 90’s intrinsic functions, but they’re not quite the same. Why? Because Fortran 90’s intrinsic functions are built directly into the language, while C’s library functions are not really built into the language as such; you could replace them with your own if you wanted. Here’s some example standard library functions in C: Function Return Type Return Value #include file printf int number of characters written stdio.h Print (output) to standard output (the terminal) in the given format scanf int number of items input stdio.h Scan (input) from standard input (the keyboard) in the given format isalpha int Boolean: is argument a letter? ctype.h isdigit int Boolean: is argument a digit? ctype.h strcpy char [ ] string containing copy string.h Copy a string into another (empty) string strcmp int comparison of two strings string.h Lexical comparison of two strings; result is index in which strings differ: negative value if first string less than second, positive if vice versa, zero if equal sqrt float square root of argument math.h pow float 1st argument raised to 2nd argument math.h 1 Brian W. -
A Framework for the Development of Multi-Level Reflective Applications
A Framework for the Development of Multi-Level Reflective Applications Federico Valentino, Andrés Ramos, Claudia Marcos and Jane Pryor ISISTAN Research Institute Fac. de Ciencias Exactas, UNICEN Pje. Arroyo Seco, B7001BBO Tandil, Bs. As., Argentina Tel/Fax: +54-2293-440362/3 E-mail: {fvalenti,aramos,cmarcos,jpryor}@exa.unicen.edu.ar URL: http://www.exa.unicen.edu.ar/~isistan Abstract. Computational reflection has become a useful technique for developing applications that are able to observe and modify their behaviour. Reflection has evolved to the point where it is being used to address a variety of application domains. This paper presents a reflective architecture that has been developed as a framework that provides a flexible reflective mechanism for the development of a wide range of applications. This architecture supports many meta-levels, where each one may contain one or more planes. A plane groups components that deal with the same functionality, and so enhances the separation of concerns in the system. The reflective mechanism permits different types of reflection, and also incorporates the runtime handling of potential conflicts between competing system components. The design and implementation of this framework are described, and an example illustrates its characteristics. 1. Introduction Reflective architectures provide a degree of flexibility that allows designers to adapt and add functionality to software systems in a transparent fashion. Since its onset, computational reflection has been proposed and used for the solving of many different problem domains in software engineering: aspect-oriented programming [PDF99, PBC00], multi-agent systems [Zun00], concurrency programming [WY88, MMY93], distributed systems [Str93, OI94, OIT92], and others. -
Support for Understanding and Writing Exception Handling Code
Moonstone: Support for Understanding and Writing Exception Handling Code Florian Kistner,y Mary Beth Kery,z Michael Puskas,x Steven Moore,z and Brad A. Myersz fl[email protected], [email protected], [email protected], [email protected], [email protected] y Department of Informatics, Technical University of Munich, Germany z Human-Computer Interaction Institute, Carnegie Mellon University, Pittsburgh, PA, USA x School of Computing, Informatics, and Decision Systems Engineering, Arizona State University, Tempe, AZ, USA Abstract—Moonstone is a new plugin for Eclipse that supports developers in understanding exception flow and in writing excep- tion handlers in Java. Understanding exception control flow is paramount for writing robust exception handlers, a task many de- velopers struggle with. To help with this understanding, we present two new kinds of information: ghost comments, which are transient overlays that reveal potential sources of exceptions directly in code, and annotated highlights of skipped code and associated handlers. To help developers write better handlers, Moonstone additionally provides project-specific recommendations, detects common bad practices, such as empty or inadequate handlers, and provides automatic resolutions, introducing programmers to advanced Java exception handling features, such as try-with- resources. We present findings from two formative studies that informed the design of Moonstone. We then show with a user study that Moonstone improves users’ understanding in certain Fig. 1. Overview of Moonstone’s features. areas and enables developers to amend exception handling code more quickly and correctly. it difficult to assess the behavior of the software system [1]. While novices particularly struggle with exception handling I. -
Programming with Exceptions in Jcilk$
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Science of Computer Programming 63 (2006) 147–171 www.elsevier.com/locate/scico Programming with exceptions in JCilk$ John S. Danaher, I.-Ting Angelina Lee∗, Charles E. Leiserson Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA Received 29 December 2005; received in revised form 7 May 2006; accepted 18 May 2006 Available online 25 September 2006 Abstract JCilk extends the serial subset of the Java language by importing the fork-join primitives spawn and sync from the Cilk multithreaded language, thereby providing call-return semantics for multithreaded subcomputations. In addition, JCilk transparently integrates Java’s exception handling with multithreading by extending the semantics of Java’s try and catch constructs, but without adding new keywords. This extension is “faithful” in that it obeys Java’s ordinary serial semantics when executed on a single processor. When executed in parallel, however, an exception thrown by a JCilk computation causes its sibling computations to abort, which yields a clean semantics in which the enclosing cilk try block need only handle a single exception. The exception semantics of JCilk allows programs with speculative computations to be programmed easily. Speculation is essential in order to parallelize programs such as branch-and-bound or heuristic search. We show how JCilk’s linguistic mechanisms can be used to program the “queens” puzzle and a parallel alpha–beta search. We have implemented JCilk’s semantic model in a prototype compiler and runtime system, called JCilk-1. -
CS 6110 S11 Lecture 15 Exceptions and First-Class Continuations 26 February 2010
CS 6110 S11 Lecture 15 Exceptions and First-Class Continuations 26 February 2010 1 CPS and Strong Typing Now let us use CPS semantics to augment our previously defined FL language translation so that it supports runtime type checking. This time our translated expressions will be functions of ρ and k denoting an environment and a continuation, respectively. The term E[[e]]ρk represents a program that evaluates e in the environment ρ and sends the resulting value to the continuation k. As before, assume that we have an encoding of variable names x and a representation of environments ρ along with lookup and update functions lookup ρ x and update ρ x v. In addition, we want to catch type errors that may occur during evaluation. As before, we use integer tags to keep track of types: 4 4 4 Err = 0 Null = 1 Bool = 2 4 4 4 Num = 3 Tuple = 4 Func = 5 A tagged value is a value paired with its type tag; for example, (0; true). Using these tagged values, we can now define a translation that incorporates runtime type checking: 4 E[[x]]ρk = k (lookup ρ x) 4 E[[b]]ρk = k (Bool; b) 4 E[[n]]ρk = k (Num; n) 4 E[[nil]]ρk = k (Null; 0) 4 E[[(e1; : : : ; en)]]ρk = E[[e1 ]]ρ(λv1 :::: E[[e2 ]]ρ(λv2 :::: [[E ]]en ρ(λvn : k (Tuple; n; (v1; : : : ; vn))))) 4 E[[let x = e1 in e2 ]]ρk = E[[e1 ]]ρ(λp: E[[e2 ]] (update ρ x p) k) 4 E[[λx: e]]ρk = k (Func; λxk: E[[e]](update ρ x x)k) 4 E[[error]]ρk = k (Err; error): Now a function application can check that it is actually applying a function: 4 E[[e0 e1 ]]ρk = E[[e0 ]]ρ(λp: let (t; f) = p in if t =6 Func then error else E[[e1 ]]ρ(λv: fvk)) We can simplify this by defining a helper function check-fn: 4 check-fn = λkp: let (t; f) = p in if t =6 Func then error else kf: The helper function takes in a continuation and a tagged value, checks the type, strips off the tag, and passes the raw (untagged) value to the continuation. -
Python 3 Types in the Wild:A Tale of Two Type Systems
Python 3 Types in the Wild: A Tale of Two Type Systems Ingkarat Rak-amnouykit Daniel McCrevan Ana Milanova Rensselaer Polytechnic Institute Rensselaer Polytechnic Institute Rensselaer Polytechnic Institute New York, USA New York, USA New York, USA [email protected] [email protected] [email protected] Martin Hirzel Julian Dolby IBM TJ Watson Research Center IBM TJ Watson Research Center New York, USA New York, USA [email protected] [email protected] Abstract ACM Reference Format: Python 3 is a highly dynamic language, but it has introduced Ingkarat Rak-amnouykit, Daniel McCrevan, Ana Milanova, Martin a syntax for expressing types with PEP484. This paper ex- Hirzel, and Julian Dolby. 2020. Python 3 Types in the Wild: A Tale of Two Type Systems. In Proceedings of the 16th ACM SIGPLAN plores how developers use these type annotations, the type International Symposium on Dynamic Languages (DLS ’20), Novem- system semantics provided by type checking and inference ber 17, 2020, Virtual, USA. ACM, New York, NY, USA, 14 pages. tools, and the performance of these tools. We evaluate the https://doi.org/10.1145/3426422.3426981 types and tools on a corpus of public GitHub repositories. We review MyPy and PyType, two canonical static type checking 1 Introduction and inference tools, and their distinct approaches to type Dynamic languages in general and Python in particular1 analysis. We then address three research questions: (i) How are increasingly popular. Python is particularly popular for often and in what ways do developers use Python 3 types? machine learning and data science2. A defining feature of (ii) Which type errors do developers make? (iii) How do type dynamic languages is dynamic typing, which, essentially, for- errors from different tools compare? goes type annotations, allows variables to change type and Surprisingly, when developers use static types, the code does nearly all type checking at runtime. -
The Grace Programming Language Draft Specification Version 0.5. 2025" (2015)
Portland State University PDXScholar Computer Science Faculty Publications and Presentations Computer Science 2015 The Grace Programming Language Draft Specification ersionV 0.5. 2025 Andrew P. Black Portland State University, [email protected] Kim B. Bruce James Noble Follow this and additional works at: https://pdxscholar.library.pdx.edu/compsci_fac Part of the Programming Languages and Compilers Commons Let us know how access to this document benefits ou.y Citation Details Black, Andrew P.; Bruce, Kim B.; and Noble, James, "The Grace Programming Language Draft Specification Version 0.5. 2025" (2015). Computer Science Faculty Publications and Presentations. 140. https://pdxscholar.library.pdx.edu/compsci_fac/140 This Working Paper is brought to you for free and open access. It has been accepted for inclusion in Computer Science Faculty Publications and Presentations by an authorized administrator of PDXScholar. Please contact us if we can make this document more accessible: [email protected]. The Grace Programming Language Draft Specification Version 0.5.2025 Andrew P. Black Kim B. Bruce James Noble April 2, 2015 1 Introduction This is a specification of the Grace Programming Language. This specifica- tion is notably incomplete, and everything is subject to change. In particular, this version does not address: • James IWE MUST COMMIT TO CLASS SYNTAX!J • the library, especially collections and collection literals • static type system (although we’ve made a start) • module system James Ishould write up from DYLA paperJ • dialects • the abstract top-level method, as a marker for abstract methods, • identifier resolution rule. • metadata (Java’s @annotations, C] attributes, final, abstract etc) James Ishould add this tooJ Kim INeed to add syntax, but not necessarily details of which attributes are in language (yet)J • immutable data and pure methods.