30 lines
1.6 KiB
Text
30 lines
1.6 KiB
Text
PLY is a 100% Python implementation of the common parsing tools lex and yacc.
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Here are a few highlights:
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- PLY is very closely modeled after traditional lex/yacc. If you know how to
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use these tools in C, you will find PLY to be similar.
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- PLY provides *very* extensive error reporting and diagnostic information to
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assist in parser construction. The original implementation was developed
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for instructional purposes. As a result, the system tries to identify the
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most common types of errors made by novice users.
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- PLY provides full support for empty productions, error recovery, precedence
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specifiers, and moderately ambiguous grammars.
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- Parsing is based on LR-parsing which is fast, memory efficient, better
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suited to large grammars, and which has a number of nice properties when
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dealing with syntax errors and other parsing problems. Currently, PLY builds
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its parsing tables using the LALR(1) algorithm used in yacc.
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- PLY uses Python introspection features to build lexers and parsers. This
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greatly simplifies the task of parser construction since it reduces the
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number of files and eliminates the need to run a separate lex/yacc tool
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before running your program.
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- PLY can be used to build parsers for "real" programming languages. Although
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it is not ultra-fast due to its Python implementation, PLY can be used to
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parse grammars consisting of several hundred rules (as might be found for a
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language like C). The lexer and LR parser are also reasonably efficient
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when parsing typically sized programs. People have used PLY to build
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parsers for C, C++, ADA, and other real programming languages.
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