![]() ![]() If Symantec Cafe version 1.2 or later is installed, you can type these commands: C:> path C:\cafe\java\bin %path% If you have the Sun JDK installed, you can type these commands: C:> path C:\java\bin %path%Ĭ:> set CLASSPATH=. If the above command did not work, or if you aren't sure whether or not you have things set up properly, open an MS-DOS window by traversing the Start->Programs->MS-DOS Prompt menu items. The command shown above assumes that the java command is in your command path and that the class path has been set up appropriately. To install Jack you need to invoke this install class, which, on a Windows 95 machine is done using the command: C:>java install. This comes to you in the form of a self-unpacking Java class called install. First you download a copy from the Jack home page. Getting ahold of Jack is also quite easy. jack file and run the tool, and it gives you back a Java class that will parse that grammar. Jack is an exceptionally easy tool to describe: Simply put, you give it a set of combined grammatical and lexing rules in the form of a. Jack (rhymes with yacc) is a parser generator, in the spirit of PCCTS, that Sun has released for free to the Java programming community. Combined with the rapid development cycle of Java, automatic parser generation provides a tool for compiler design that is hard to beat. As the requirement to parse text input comes up again and again, automatic parser generation rates pretty highly in my toolbox. I rate tools by the generality of the problem they solve. This can be a tremendous time-saver in both simple and complex projects. The power of automatic parser generation is that it allows users to concentrate on the grammar and not worry about the correctness of the implementation. PCCTS quickly developed a following of folks who found its files easier to use than yacc. ![]() This understanding can be essential when trying to diagnose errors in the grammar specification. By generating code that is easier to read, PCCTS makes it easier for a human reading the code to understand what the various pieces are doing. Furthermore, the code that PCCTS generates is much more readable than the code generated by yacc. Two components of PCCTS - DFA and ANTLR - provide the same functions as lex and yacc however the grammars that ANTLR accepts are LL(k) grammars as opposed to the LALR grammars used by yacc. The world of automatic parser generation advanced again when Terrence Parr, then a student at Purdue University, created the Purdue Compiler Construction Tool Set or PCCTS. ![]() I used lex and yacc, and in less than a week my compiler was up and running! Later, the Free Software Foundation's GNU project produced "improved" versions of lex and yacc - named flex and bison - for use on platforms that did not run a derivative of the Unix operating system. Lex built lexical analyzers from regular expressions, and yacc reduced a grammar specification into a table-driven compiler that could produce code when it had successfully parsed productions from that grammar. Then a friend showed me the Unix utilities lex and yacc. I started with a freshly composed grammar and prepared to launch into the multiweek project of putting together a compiler. In my first "real" job after college, I got an assigment to create a new graphics processing language to compile into commands for a graphics coprocessor. I remember feeling very accomplished at that point. With the help of my wife to be, I had written a simple compiler that could turn programs written in a language made up for the class into executable programs. I distinctly remember my introduction to automatic parser generation: In college I had completed a class on compiler construction. It converts text that can be read by humans into data structures known as parse trees, which are understood by the computer. Automatic compiler parser generationĪ parser is one of the most common components of a computer application. Then the article will focus on Jack and how you can use it to generate parsers and applications built with those parsers, based on your high-level grammar. The first part of the article covers a brief introduction to automatic parser generation, and my first experiences with them. This article will serve as an introduction to this new tool. Sun has released Jack, a new tool written in Java that automatically generates parsers by compiling a high-level grammar specification stored in a text file. ![]()
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