Grammar Spec (gspec) Processing Tool

This directory contains a simple tool for processing programming-language grammar specifications. The idea is to allow a single specification to be used to generate multiple textual representations (e.g., LaTex and Asciidoc).

Notation

symbol names: symbol names are identifiers that start with a letter and can contain letters, decimal digits, dashes ('-'), underscores ('_'), and single quotes (''').
literal terminal symbols: a literal terminal is specified by enclosing it in single quote characters; e.g., 'if'.
terminal symbols: a terminal symbol name enclosed in double quotes; e.g., "identifier".
non-terminal symbols: a non-terminal symbol name enclosed in angle brackets; e.g., <expression>.
labels are identifiers enclosed in [ ]
comments start with the # character and run to the end of the current line. There is a special form of a comment, called a note, that starts with the characters #< and which is attached to the proceeding production.

Syntax

The following grammar (specified using the above notation) describes the syntax of grammar specs:

[gspec] {
  <spec>    : <content>

  <content> : <section>+
            | <rule>+

  <section> : "label" '{' <content> '}'

  <rule>    : "label"? "non-term" ':' <rhs> ( '|' <rhs> )*

  <rhs>     : "label"? 'empty' "note"?
            | "label"? <phrase>+ "note"?

  <phrase>  : <symbol>
            | <symbol> <repeat>
            | '(' <phrase>+ ')' <repeat>

  <symbol>  : "non-terminal"
            | "terminal"
            | "literal"

  <repeat>  : " '?' | '*' | '+'
}

Grammar Sections

A grammar can be specified as a sequence of CFG rules or as a heirarchy of labeled sections, where the innermost sections contain CFG rules.

Sections provide a mechanism for splitting a specification across multiple output files. For example, if we have a grammar specification in the file lang.gspec that has the following structure

[foo] {
  [bar] { ... }
  [baz] { ... }
}

then there will be two output files generated: lang-foo-bar.out and lang-foo-baz.out (where out is the file suffix for the target format).

Targets

We currently envision three targets for the gspec tool (of which two are currently implemented). These are

LaTeX using the grammar.sty file that is provided in the support directory
LaTeX using the syntax.sty package that comes with most TeX distributions. (not yet implemented)
HTML via asciidoctor. This target produces Asciidoc files that can be used to generate HTML. The grammar.css support file defines styles for the different kinds of grammar symbols.

JohnReppy/gspec

Grammar Spec (gspec) Processing Tool

Notation

Syntax

Grammar Sections

Targets