pyPEG 1.4 released

Volker Birk bumens at dingens.org
Wed Aug 3 17:56:12 CEST 2011


New: This release fixes some bugs with packrat parsing.

Homepage: http://fdik.org/pyPEG
Download: http://fdik.org/pyPEG/pyPEG.py

Python is a nice scripting language. It even gives you access to it's
own parser and compiler. It also gives you access to different other
parsers for special purposes like XML and string templates.

But sometimes you may want to have your own parser. This is what's pyPEG
for. And pyPEG supports Unicode. 

What is PEG?

PEG means Parsing Expression Grammar. It's something like the idea of
Regular Expressions for context free languages; a very clear explanation
you'll find in the Wikipedia article about PEG.

With PEGs you can describe the same languages like with BNF (and they're
even similar).

What is a Parser-Interpreter?

Common parsers are not using PEGs and top-down parsing, but LR(n) or
LL(n) and bottom-up parsing. This results in the idea of implementing
parser generators.

Because with LR(n) or LL(n) parsers you need to calculate out a DFA
first, usually you let the parser generator do this for you. The result
is a parser implementation for your BNF grammar, which was the input.
One could call a parser generator a compiler from BNF to a parser
implementation.

A Parser-Interpreter does work as an interpreter instead of being such a
compiler. Just give your grammar as input, and it parses the described
language out of text. There will be no program generated.

VB.
-- 
Volker Birk, Nobelstrasse 32, D-88131 Lindau (Bodensee), EU,
Erde, Solar-System, Orion Arm, Milchstrasse, Lokale Gruppe,
Virgo-Superhaufen, Coma-Virgo-Filament. mailto:dingens at bumens.org
http://fdik.org  D-IRCNet fdik!vb at wallaby.dingens.org


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