Applications of Regular Expressions and Finite Automata: Lexical Analysis

2014 ◽  
pp. 81-92
Keyword(s):  
Finite Automata ◽  
Regular Expressions ◽  
Lexical Analysis

scholarly journals An Fuzzy Lexical Research

2019 ◽  
Vol 8 (6S3) ◽  
pp. 1209-1211
Keyword(s):  
Finite Automata ◽  
String Matching ◽  
Regular Languages ◽  
Regular Expressions ◽  
Lexical Analysis ◽  
Design And Implementation ◽  
Comprehensive View ◽  
Analysis Phase ◽  
Source Program ◽  
Degree Of Membership

The objective of this paper is to analyse the design and implementation of the fuzzy lexical analyser and observe how it is different from the traditional lexical analyser. It is known that lexical analysis is an important phase of a compiler. It reads the source program character by character and uses regular expressions, finite automata methods for string matching. Unlike traditional lexical analysers, tokens in fuzzy analysers belong to more than one token type with varying degree of membership. The paper exchange views on the design and implementation of fuzzy lexical analysers. It observes algorithms that handle errors due to insertion, deletion etc. in the lexical analysis phase of a compiler. Several properties of fuzzy languages are also reviewed. Hence this paper gives a comprehensive view of fuzzy regular languages, models and algorithms

scholarly journals Software Toolchain for Large-Scale RE-NFA Construction on FPGA

2009 ◽  
Vol 2009 ◽  
pp. 1-10 ◽  
Author(s):  
Yi-Hua E. Yang ◽  
Viktor K. Prasanna
Keyword(s):  
High Performance ◽  
Large Scale ◽  
Regular Expression ◽  
Finite Automata ◽  
Fixed Number ◽  
Regular Expressions ◽  
Pattern Complexity ◽  
Regular Expression Matching ◽  
Area Increase ◽  
Prototype Software

We present a software toolchain for constructing large-scaleregular expression matching(REM) on FPGA. The software automates the conversion of regular expressions into compact and high-performance nondeterministic finite automata (RE-NFA). Each RE-NFA is described as an RTL regular expression matching engine (REME) in VHDL for FPGA implementation. Assuming a fixed number of fan-out transitions per state, ann-statem-bytes-per-cycle RE-NFA can be constructed inO(n×m)time andO(n×m)memory by our software. A large number of RE-NFAs are placed onto a two-dimensionalstaged pipeline, allowing scalability to thousands of RE-NFAs with linear area increase and little clock rate penalty due to scaling. On a PC with a 2 GHz Athlon64 processor and 2 GB memory, our prototype software constructs hundreds of RE-NFAs used by Snort in less than 10 seconds. We also designed a benchmark generator which can produce RE-NFAs with configurable pattern complexity parameters, including state count, state fan-in, loop-back and feed-forward distances. Several regular expressions with various complexities are used to test the performance of our RE-NFA construction software.

scholarly journals Extended to multi-tilde–bar regular expressions and efficient finite automata constructions

2015 ◽  
Vol 33 ◽  
pp. 58-70
Author(s):  
Faissal Ouardi ◽  
Jean-Marc Champarnaud ◽  
Djelloul Ziadi
Keyword(s):  
Finite Automata ◽  
Regular Expressions

ANTIMIROV AND MOSSES'S REWRITE SYSTEM REVISITED

2009 ◽  
Vol 20 (04) ◽  
pp. 669-684 ◽  
Author(s):  
MARCO ALMEIDA ◽  
NELMA MOREIRA ◽  
ROGÉRIO REIS
Keyword(s):  
Finite Automata ◽  
Functional Approach ◽  
Regular Expressions ◽  
Average Case ◽  
Deterministic Finite Automata ◽  
Preliminary Results ◽  
Functional Version ◽  
Comparative Results ◽  
Rewrite System ◽  
Extended Regular Expressions

Antimirov and Mosses proposed a rewrite system for deciding the equivalence of two (extended) regular expressions. They argued that this method could lead to a better average-case algorithm than those based on the comparison of the equivalent minimal deterministic finite automata. In this paper we present a functional approach to that method, prove its correctness, and give some experimental comparative results. Besides an improved functional version of Antimirov and Mosses's algorithm, we present an alternative one using partial derivatives. Our preliminary results lead to the conclusion that, indeed, these methods are feasible and, most of the time, faster than the classical methods.

From regular expressions to finite automata∗

1999 ◽  
Vol 72 (4) ◽  
pp. 415-431 ◽  
Author(s):  
J.-M. Champarnaud ◽  
J.-L. Ponty ◽  
D. Ziadi
Keyword(s):  
Finite Automata ◽  
Regular Expressions

scholarly journals Regular Expressions with Lookahead

2021 ◽  
Vol 27 (4) ◽  
pp. 324-340
Author(s):  
Martin Berglund ◽  
Brink van der Merwe ◽  
Steyn van Litsenborgh
Keyword(s):  
Finite Automata ◽  
The State ◽  
Regular Expressions ◽  
Deterministic Finite Automata ◽  
State Complexity

This paper investigates regular expressions which in addition to the standard operators of union, concatenation, and Kleene star, have lookaheads. We show how to translate regular expressions with lookaheads (REwLA) to equivalent Boolean automata having at most 3 states more than the length of the REwLA. We also investigate the state complexity when translating REwLA to equivalent deterministic finite automata (DFA).

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