Waving A Language-Independent WEB

نویسندگان

  • Christopher J. Van Wyk
  • Norman Ramsey
چکیده

In the fall of 1987 I started planning the implementation of a suite of tools for building veriied Ada programs Ramsey 89]. The rst tool to be built was a veriication condition generator, which was to be formally deened using the typed lambda calculus. I was eager to include the deenition with the code so that it would be easy to check the code's correctness. Using WEB would have made this easy, but, unfortunately, the target programming language was SSL (a language for specifying structure editors), and the only languages for which WEB implementations were available were Pascal and C. Writing a new WEB from scratch didn't make sense, so I decided to modify Silvio Levy's implementation of WEB in C Levy 87], to get a WEB that would be written in C, but would read and write SSL code. From my previous experiences modifying WEB, I knew that the most time-consuming job would be ne-tuning the grammar that WEAVE uses to prettyprint code. I believed I could make debugging that grammar a lot less painful if, instead of trying to make dozens of small modiications by hand, I wrote a simple program, perhaps an AWK script, that would read a description of the grammar and generate C code for WEAVE. That AWK script became SPIDER, a program that turns language descriptions into C code for TANGLE and WEAVE. I have used SPIDER to generate WEBs for C, AWK, SSL, Ada, and a couple of other languages. I won't go into the details of SPIDER; instead, I'll try to describe what SPIDER does to accomplish its mission, or how to take the \essence of WEB" and make it language-independent. When using WEB, a programmer writes a single source le, foo.web, that holds both code and documentation. TANGLE and WEAVE read that le. TANGLE extracts the code from the WEB le and rewrites it in a form suitable for compiling. WEAVE passes the documentation parts to a document formatter (T E X), and prettyprints the code parts. The whole process is shown in Figure 1, for C programs written in WEB. The x represents les that have to be written by

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عنوان ژورنال:
  • Commun. ACM

دوره 32  شماره 

صفحات  -

تاریخ انتشار 1989