Lexical Nesting
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Chapter 5 Names, Bindings, and Scopes
Chapter 5 Names, Bindings, and Scopes 5.1 Introduction 198 5.2 Names 199 5.3 Variables 200 5.4 The Concept of Binding 203 5.5 Scope 211 5.6 Scope and Lifetime 222 5.7 Referencing Environments 223 5.8 Named Constants 224 Summary • Review Questions • Problem Set • Programming Exercises 227 CMPS401 Class Notes (Chap05) Page 1 / 20 Dr. Kuo-pao Yang Chapter 5 Names, Bindings, and Scopes 5.1 Introduction 198 Imperative languages are abstractions of von Neumann architecture – Memory: stores both instructions and data – Processor: provides operations for modifying the contents of memory Variables are characterized by a collection of properties or attributes – The most important of which is type, a fundamental concept in programming languages – To design a type, must consider scope, lifetime, type checking, initialization, and type compatibility 5.2 Names 199 5.2.1 Design issues The following are the primary design issues for names: – Maximum length? – Are names case sensitive? – Are special words reserved words or keywords? 5.2.2 Name Forms A name is a string of characters used to identify some entity in a program. Length – If too short, they cannot be connotative – Language examples: . FORTRAN I: maximum 6 . COBOL: maximum 30 . C99: no limit but only the first 63 are significant; also, external names are limited to a maximum of 31 . C# and Java: no limit, and all characters are significant . C++: no limit, but implementers often impose a length limitation because they do not want the symbol table in which identifiers are stored during compilation to be too large and also to simplify the maintenance of that table. -
By Kumari Priyadarshani 22-04-2020 BBM 3Rd Year Variables in C a Variable Is a Name of the Memory Location. It Is Used to Store Data
By Kumari priyadarshani 22-04-2020 BBM 3rd year Variables in C A variable is a name of the memory location. It is used to store data. Its value can be changed, and it can be reused many times. It is a way to represent memory location through symbol so that it can be easily identified. Let's see the syntax to declare a variable: type variable_list; The example of declaring the variable is given below: int a; float b; char c; Here, a, b, c are variables. The int, float, char are the data types. We can also provide values while declaring the variables as given below: int a=10,b=20;//declaring 2 variable of integer type float f=20.8; char c='A'; Rules for defining variables A variable can have alphabets, digits, and underscore. A variable name can start with the alphabet, and underscore only. It can't start with a digit. No whitespace is allowed within the variable name. A variable name must not be any reserved word or keyword, e.g. int, float, etc. Valid variable names: int a; int _ab; int a30; Invalid variable names: int 2; int a b; int long; Types of Variables in C There are many types of variables in c: local variable global variable static variable automatic variable external variable 1)Local Variable A variable that is declared inside the function or block is called a local variable. It must be declared at the start of the block. void function1(){ int x=10;//local variable } You must have to initialize the local variable before it is used. -
7. Functions in PHP – II
7. Functions in PHP – II Scope of variables in Function Scope of variable is the part of PHP script where the variable can be accessed or used. PHP supports three different scopes for a variable. These scopes are 1. Local 2. Global 3. Static A variable declared within the function has local scope. That means this variable is only used within the function body. This variable is not used outside the function. To demonstrate the concept, let us take an example. // local variable scope function localscope() { $var = 5; //local scope echo '<br> The value of $var inside the function is: '. $var; } localscope(); // call the function // using $var outside the function will generate an error echo '<br> The value of $var inside the function is: '. $var; The output will be: The value of $var inside the function is: 5 ( ! ) Notice: Undefined variable: var in H:\wamp\www\PathshalaWAD\function\function localscope demo.php on line 12 Call Stack # Time Memory Function Location 1 0.0003 240416 {main}( ) ..\function localscope demo.php:0 The value of $var inside the function is: Page 1 of 7 If a variable is defined outside of the function, then the variable scope is global. By default, a global scope variable is only available to code that runs at global level. That means, it is not available inside a function. Following example demonstrate it. <?php //variable scope is global $globalscope = 20; // local variable scope function localscope() { echo '<br> The value of global scope variable is :'.$globalscope; } localscope(); // call the function // using $var outside the function will generate an error echo '<br> The value of $globalscope outside the function is: '. -
Object Lifetimes In
Object Lifetimes in Tcl - Uses, Misuses, Limitations By Phil Brooks - Mentor – A Siemens Corporation Presented at the 25 nd annual Tcl/Tk conference, Houston Texas, November 2018 Mentor – A Siemens Corporation 8005 Boeckman Road Wilsonville, Oregon 97070 [email protected] Abstract: The management of the lifetime of an object in Tcl presents a number of unique challenges. In the C++ world, the technique of Resource Allocation is Initialization (RAII) is commonly used to control the lifetime of certain objects. With this technique, an object on the call stack is used to insure proper cleanup of a resource. When the object goes out of scope, the resource is released. It presents a low overhead mechanism for a garbage collection like facility without the complication of more complete garbage collection systems. Tcl doesn't have a similar direct capability, and the need for it has resulted in two techniques that are commonly used to substitute for the capability. The techniques are: 1) Use of the trace command to catch unset of a variable. 2) Mis-use of the lifetime of a Tcl_Obj created with Tcl_NewObj. Each of these techniques has drawbacks. The primary issue with the trace technique is that it requires the user of an object to arrange for explicit destruction of the object. This makes the interface more error prone. The mis-use of lifetime of a Tcl_Obj is subject to premature cleanup of the resource if the object is shimmered to a string for any reason. This paper surveys these lifetime management patterns and demonstrates the use of a new user level technique for lifetime management. -
An Empirical Study Into COBOL Type Inferencing*
Science of Computer Programming ELSEVIERI Science of Computer Programming 40 (2001) 189-211 www.elsevier.nl/locate/scico An empirical study into COBOL type inferencing* Arie van Deursen 1, Leon Moonen 1 * CWL P. 0. Box 94079, 1090 GB Amsterdam, Netherlands Accepted 2 February 2001 Abstract In a typical COBOL program, the data division consists of 50% of the lines of code. Automatic type inference can help to understand the large collections of variable declarations contained therein, showing how variables are related based on their actual usage. The most problematic aspect of type inference is pollution, the phenomenon that types become too large, and contain variables that intuitively should not belong to the same type. The aim of the paper is to provide empirical evidence for the hypothesis that the use of subtyping is an effective way for dealing with pollution. The main results include a tool set to carry out type inference experiments, a suite of metrics characterizing type inference outcomes, and the experimental observation that only one instance of pollution occurs in the case study conducted. @ 2001 Elsevier Science B.V. All rights reserved. Keywords: Software maintenance; Static program analysis; Variable usage; Case study 1. Introduction In this paper, we will be concerned with the variables occurring in a COBOL pro gram. The two main parts of a COBOL program are the data division, containing declarations for all variables used, and the procedure division, which contains the state ments performing the program's functionality. Since it is in the procedure division that the actual computations are made, one would expect this division to be larger than the data division. -
Declare Function Inside a Function Python
Declare Function Inside A Function Python Transisthmian and praetorian Wye never ensphere helter-skelter when Shawn lord his nightshade. Larboard Hal rumors her dizziesacapnia very so encouragingly actinally. that Colbert aurifies very inferentially. Kenyan Tad reframes her botts so irefully that Etienne Closures prove to it efficient way something we took few functions in our code. Hope you have any mutable object. Calling Functions from Other Files Problem Solving with Python. What embassy your website look like? Then you can declare any result of a million developers have been loaded? The coach who asked this gas has marked it as solved. We focus group functions together can a Python module see modules and it this way lead our. What are Lambda Functions and How to Use Them? It working so art the result variable is only accessible inside the function in. Variables inside python node, learn more detail, regardless of instances of a program demonstrates it. The python function inside another, which start here, and beginners start out. Get code examples like python define a function within a function instantly right anytime your google search results with the Grepper Chrome. The function by replacing it contains one function start here are discussed: how do not provide extremely cost efficient as their name? How to the page helpful for case it requires you can declare python data science. Each item from the python function has arbitrary length arguments must first, but are only the output is simply the function to. We declare their perfomance varies with the gathered arguments using a wrapped the arguments does the computed fahrenheit to declare function inside a function python? List of python can declare a function inside a million other functions we declare function inside a function python. -
A Concurrent PASCAL Compiler for Minicomputers
512 Appendix A DIFFERENCES BETWEEN UCSD'S PASCAL AND STANDARD PASCAL The PASCAL language used in this book contains most of the features described by K. Jensen and N. Wirth in PASCAL User Manual and Report, Springer Verlag, 1975. We refer to the PASCAL defined by Jensen and Wirth as "Standard" PASCAL, because of its widespread acceptance even though no international standard for the language has yet been established. The PASCAL used in this book has been implemented at University of California San Diego (UCSD) in a complete software system for use on a variety of small stand-alone microcomputers. This will be referred to as "UCSD PASCAL", which differs from the standard by a small number of omissions, a very small number of alterations, and several extensions. This appendix provides a very brief summary Of these differences. Only the PASCAL constructs used within this book will be mentioned herein. Documents are available from the author's group at UCSD describing UCSD PASCAL in detail. 1. CASE Statements Jensen & Wirth state that if there is no label equal to the value of the case statement selector, then the result of the case statement is undefined. UCSD PASCAL treats this situation by leaving the case statement normally with no action being taken. 2. Comments In UCSD PASCAL, a comment appears between the delimiting symbols "(*" and "*)". If the opening delimiter is followed immediately by a dollar sign, as in "(*$", then the remainder of the comment is treated as a directive to the compiler. The only compiler directive mentioned in this book is (*$G+*), which tells the compiler to allow the use of GOTO statements. -
Open Office Specification 1.0
Open Office Specification 1.0 Committee Draft 1, 22 Mar 2004 Document identifier: office-spec-1.0-cd-1.sxw Location: http://www.oasis-open.org/committees/office/ Editors: Michael Brauer, Sun Microsystems <[email protected]> Gary Edwards <[email protected]> Daniel Vogelheim, Sun Microsystems <[email protected]> Contributors: Doug Alberg, Boeing <[email protected]> Simon Davis, National Archive of Australia <[email protected]> Patrick Durusau, Society of Biblical Literature <[email protected]> David Faure, <[email protected]> Paul Grosso, Arbortext <[email protected]> Tom Magliery, Blast Radius <[email protected]> Phil Boutros, Stellent <[email protected]> John Chelsom, CSW Informatics <[email protected]> Jason Harrop, SpeedLegal <[email protected]> Mark Heller, New York State Office of the Attorney General <[email protected]> Paul Langille, Corel <[email protected]> Monica Martin, Drake Certivo <[email protected]> Uche Ogbuji <[email protected]> Lauren Wood <[email protected]> Abstract: This is the specification of Open Office XML, an open, XML-based file format for office applications, based on OpenOffice.org XML [OOo]. Status: This document is a draft, and will be updated periodically on no particular schedule. Send comments to the editors. Committee members should send comments on this specification to the [email protected] list. Others should subscribe to and send comments to the [email protected] list. To subscribe, send an email message to office- [email protected] with the word "subscribe" as the body of the message. -
XL C/C++: Language Reference About This Document
IBM XL C/C++ for Linux, V16.1.1 IBM Language Reference Version 16.1.1 SC27-8045-01 IBM XL C/C++ for Linux, V16.1.1 IBM Language Reference Version 16.1.1 SC27-8045-01 Note Before using this information and the product it supports, read the information in “Notices” on page 63. First edition This edition applies to IBM XL C/C++ for Linux, V16.1.1 (Program 5765-J13, 5725-C73) and to all subsequent releases and modifications until otherwise indicated in new editions. Make sure you are using the correct edition for the level of the product. © Copyright IBM Corporation 1998, 2018. US Government Users Restricted Rights – Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp. Contents About this document ......... v Chapter 4. IBM extension features ... 11 Who should read this document........ v IBM extension features for both C and C++.... 11 How to use this document.......... v General IBM extensions ......... 11 How this document is organized ....... v Extensions for GNU C compatibility ..... 15 Conventions .............. v Extensions for vector processing support ... 47 Related information ........... viii IBM extension features for C only ....... 56 Available help information ........ ix Extensions for GNU C compatibility ..... 56 Standards and specifications ........ x Extensions for vector processing support ... 58 Technical support ............ xi IBM extension features for C++ only ...... 59 How to send your comments ........ xi Extensions for C99 compatibility ...... 59 Extensions for C11 compatibility ...... 59 Chapter 1. Standards and specifications 1 Extensions for GNU C++ compatibility .... 60 Chapter 2. Language levels and Notices .............. 63 language extensions ......... 3 Trademarks ............. -
The Evolution of Lisp
1 The Evolution of Lisp Guy L. Steele Jr. Richard P. Gabriel Thinking Machines Corporation Lucid, Inc. 245 First Street 707 Laurel Street Cambridge, Massachusetts 02142 Menlo Park, California 94025 Phone: (617) 234-2860 Phone: (415) 329-8400 FAX: (617) 243-4444 FAX: (415) 329-8480 E-mail: [email protected] E-mail: [email protected] Abstract Lisp is the world’s greatest programming language—or so its proponents think. The structure of Lisp makes it easy to extend the language or even to implement entirely new dialects without starting from scratch. Overall, the evolution of Lisp has been guided more by institutional rivalry, one-upsmanship, and the glee born of technical cleverness that is characteristic of the “hacker culture” than by sober assessments of technical requirements. Nevertheless this process has eventually produced both an industrial- strength programming language, messy but powerful, and a technically pure dialect, small but powerful, that is suitable for use by programming-language theoreticians. We pick up where McCarthy’s paper in the first HOPL conference left off. We trace the development chronologically from the era of the PDP-6, through the heyday of Interlisp and MacLisp, past the ascension and decline of special purpose Lisp machines, to the present era of standardization activities. We then examine the technical evolution of a few representative language features, including both some notable successes and some notable failures, that illuminate design issues that distinguish Lisp from other programming languages. We also discuss the use of Lisp as a laboratory for designing other programming languages. We conclude with some reflections on the forces that have driven the evolution of Lisp. -
Chapter 5. Using Tcl/Tk
The Almagest 5-1 Chapter 5. Using Tcl/Tk Authors: Edward A. Lee Other Contributors: Brian L. Evans Wei-Jen Huang Alan Kamas Kennard White 5.1 Introduction Tcl is an interpreted “tool command language” designed by John Ousterhout while at UC Berkeley. Tk is an associated X window toolkit. Both have been integrated into Ptolemy. Parts of the graphical user interface and all of the textual interpreter ptcl are designed using them. Several of the stars in the standard star library also use Tcl/Tk. This chapter explains how to use the most basic of these stars, TclScript, as well how to design such stars from scratch. It is possible to define very sophisticated, totally customized user interfaces using this mechanism. In this chapter, we assume the reader is familiar with the Tcl language. Documentation is provided along with the Ptolemy distribution in the $PTOLEMY/tcltk/itcl/man direc- tory in Unix man page format. HTML format documentation is available from the other.src tar file in $PTOLEMY/src/tcltk. Up-to-date documentation and software releases are available by on the SunScript web page at http://www.sunscript.com. There is also a newsgroup called comp.lang.tcl. This news group accumulates a list of frequently asked questions about Tcl which is available http://www.teraform.com/%7Elvirden/tcl-faq/. The principal use of Tcl/Tk in Ptolemy is to customize the user interface. Stars can be created that interact with the user in specialized ways, by creating customized displays or by soliciting graphical inputs. 5.2 Writing Tcl/Tk scripts for the TclScript star Several of the domains in Ptolemy have a star called TclScript. -
Coding 101: Learn Ruby in 15 Minutes Visit
Coding 101: Learn Ruby in 15 minutes Visit www.makers.tech 1 Contents 2 Contents 10 Challenge 3 3 About us 11 Defining Methods 4 Installing Ruby 12 Challenge 4 4 Checking you’ve got Ruby 12 Challenge 5 5 Method calls 12 Challenge 6 5 Variables 13 Arrays 6 Truth and Falsehood 14 Hashes 7 Strings, objects and Methods 14 Challenge 7 8 Challenge 1 15 Iterations 8 Challenge 2 16 Challenge 8 9 Method Chaining 16 Challenge 9 10 Conditionals 18 Extra Challenges 2 About Us At Makers, we are creating a new generation of tech talent who are skilled and ready for the changing world of work. We are inspired by the idea of discovering and unlocking potential in people for the benefit of 21st century business and society. We believe in alternative ways to learn how to code, how to be ready for work and how to be of value to an organisation. At our core, Makers combines tech education with employment possibilities that transform lives. Our intensive four-month program (which includes a month-long PreCourse) sets you up to become a high quality professional software engineer. Makers is the only coding bootcamp with 5 years experience training software developers remotely. Your virtual experience will be exactly the same as Makers on-site, just delivered differently. If you’d like to learn more, check out www.makers.tech. 3 Installing Checking Ruby you’ve got Ruby You’ll be happy to know that Ruby comes preinstalled on all Apple computers. However we can’t simply use the system defaults - just in case we mess something up! Open the terminal on your computer and then type in If you’ve got your laptop set up already you can skip this section.