Category Archives: EasyExtend

Token Tracers

Posted on 3. June 2010 by kay

When I started programming EasyExtend in 2006 one of the major problems was the correct grammar -> NFA translation. I used big grammars and testing for correctness required lots of source code. The first heuristics I used was ugly and … Continue reading →

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Trace Based Parsing (Part V) – From Grammars to NFAs

Posted on 7. May 2009 by kay

In this article I will demonstrate the translation process by which an EBNF grammar will be translated into a Trail NFA. There are several different notations for EBNF that differ only in minor details. I’ve chosen the one of Pythons … Continue reading →

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Trace Based Parsing ( Part IV ) – Recursive NFAs

Posted on 6. May 2009 by kay

Not long ago I inserted the following piece of code in the `EasyExtend/trail/nfatracing.py` module which defines NFA tracers and cursors and deals with the reconstruction of parse trees from state set sequences. class NFAInterpreter(object): def __init__(self, nfa): for state in … Continue reading →

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Trace Based Parsing ( Part III ) – NFALexer

Posted on 4. May 2009 by kay

The NFALexer gives me an uneasy feeling. It is the most questionable of Trails components – one that cannot decide whether it wants to be a lexer that produces a token stream or a parser that produces parse trees. Continue reading →

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Trace Based Parsing ( Part II ) – NFA Expansion

Posted on 2. May 2009 by kay

In the previous article about trace based parsing (TBP) I explained the basic concepts of TBP. I motivated TBP by parse tree validators that check the correctness of parse trees against grammars and I derived a trace based LL(1) parser. … Continue reading →

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Trace Based Parsing (Part I) – Introduction

Posted on 1. May 2009 by kay

This is the first in a series of articles about Trace Based Parsing ( TBP ). Trace based parsing is a powerful top down, table driven parsing style. TBP is the technique underlying Trail which is the parser generator of … Continue reading →

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Contextual Keywords

Posted on 22. March 2009 by kay

Keywords and Contextual Keywords A language keyword is a reserved word that cannot be used as an identifier for variables, constants, classes etc. Often it is an element of language syntax. Syntactical structure is simplified by means of keywords. A … Continue reading →

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