Software visualization of LR parsing and synthesized attribute evaluation

Abstract

Visual YACC is a tool that automatically creates visualizations of the YACC LR parsing process and synthesized attribute computation. The Visual YACC tool works by instrumenting a standard YACC grammar with graphics calls that draw the appropriate data structures given the current actions by the parser. The new grammar is processed by the YACC tools and the resulting parser displays the parse stack and parse tree for every step of the parsing process of a given input string.Visual YACC was initially designed to be used in compiler construction courses to supplement the teaching of parsing and syntax directed evaluation. We have also found it to be useful in the difficult task of debugging YACC grammars. In this paper, we describe this tool and how it is used in both contexts. We also detail two different implementations of this tool: one that produces a parser written in C with calls to Motif; and a second implementation that generates Java source code.

Visual exploration of visual parser execution

“…The first tools on PL/0 [1] and CLANG [27] were hand-coded and date back to the 1980s, whereas, in the following decade, the focus was on modified compiler-compilers to generate them. These include the tools Visual YACC [35], GYACC [23], CUPV [19], VOCOCO [28], LISA [24]. In particular, CUPV is also based on CUP but discontinued.…”

CUPV—a visualization tool for generated parsers

“…Tools such as Visual Yacc [10] and Gyacc [8] were created for the purpose of visualizing parsers generated by Yacc. Other tools, such as LRParse and LLParse [4], were developed for the purpose of helping students understand parsing techniques.…”

“…The Visual Yacc tool [10] was developed as a classroom tool to assist in the teaching of grammar writing. It does not focus on displaying the actions of a parser or the content of parse tables.…”

“…It does not focus on displaying the actions of a parser or the content of parse tables. The developers of this system did discover that the tool "could be used for debugging as well as teaching," [10] but it was not developed specifically for this purpose. A Yacc parser specification must be modified by adding Motif calls before the visualization tool may be used.…”