Ragel
Encyclopedia
Ragel is a finite-state machine compiler
with output support for C
, C++
, C#, Objective-C
, D
, Java
, Go
and Ruby
source code. It supports the generation of table
or control flow
driven state machines from regular expression
s and/or state charts and can also build lexical analyser
s via the longest-match method. A unique feature of Ragel is that user actions can be associated with arbitrary state machine transitions using operators that are integrated into the regular expressions. Ragel also supports visualization of the generated machine via graphviz
.
The above graph does the following: take a user input as a series of bytes. If in 48..57 (e.g. '0' to '9') it begins like a number. If 10 is encountered, we're done. 46 is the '.' and indicates a decimal number. 69/101 is uppercase/lowercase 'e' and indicates a number in scientific format. As such it will recognize properly:
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
with output support for C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
, C++
C++
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
, C#, Objective-C
Objective-C
Objective-C is a reflective, object-oriented programming language that adds Smalltalk-style messaging to the C programming language.Today, it is used primarily on Apple's Mac OS X and iOS: two environments derived from the OpenStep standard, though not compliant with it...
, D
D (programming language)
The D programming language is an object-oriented, imperative, multi-paradigm, system programming language created by Walter Bright of Digital Mars. It originated as a re-engineering of C++, but even though it is mainly influenced by that language, it is not a variant of C++...
, Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
, Go
Go (programming language)
Go is a compiled, garbage-collected, concurrent programming language developed by Google Inc.The initial design of Go was started in September 2007 by Robert Griesemer, Rob Pike, and Ken Thompson. Go was officially announced in November 2009. In May 2010, Rob Pike publicly stated that Go was being...
and Ruby
Ruby (programming language)
Ruby is a dynamic, reflective, general-purpose object-oriented programming language that combines syntax inspired by Perl with Smalltalk-like features. Ruby originated in Japan during the mid-1990s and was first developed and designed by Yukihiro "Matz" Matsumoto...
source code. It supports the generation of table
Table (information)
A table is a means of arranging data in rows and columns.Production % of goalNorth 4087102%South 4093110% The use of tables is pervasive throughout all communication, research and data analysis. Tables appear in print media, handwritten notes, computer software, architectural...
or control flow
Control flow
In computer science, control flow refers to the order in which the individual statements, instructions, or function calls of an imperative or a declarative program are executed or evaluated....
driven state machines from regular expression
Regular expression
In computing, a regular expression provides a concise and flexible means for "matching" strings of text, such as particular characters, words, or patterns of characters. Abbreviations for "regular expression" include "regex" and "regexp"...
s and/or state charts and can also build lexical analyser
Lexical analysis
In computer science, lexical analysis is the process of converting a sequence of characters into a sequence of tokens. A program or function which performs lexical analysis is called a lexical analyzer, lexer or scanner...
s via the longest-match method. A unique feature of Ragel is that user actions can be associated with arbitrary state machine transitions using operators that are integrated into the regular expressions. Ragel also supports visualization of the generated machine via graphviz
Graphviz
Graphviz is a package of open-source tools initiated by AT&T Labs Research for drawing graphs specified in DOT language scripts. It also provides libraries for software applications to use the tools...
.
The above graph does the following: take a user input as a series of bytes. If in 48..57 (e.g. '0' to '9') it begins like a number. If 10 is encountered, we're done. 46 is the '.' and indicates a decimal number. 69/101 is uppercase/lowercase 'e' and indicates a number in scientific format. As such it will recognize properly:
2
45
055
46.
78.1
2e5
78.3e12
69.0e-3
3e+3
but not:
.3
-5
3.e2
2e5.1
See also
- Finite-state machine
- FlexFlex lexical analyserflex is a free software alternative to lex. It is frequently used with the free Bison parser generator. Unlike Bison, flex is not part of the GNU Project. Flex was written in C by Vern Paxson around 1987...
- Lex
- Regular expressionRegular expressionIn computing, a regular expression provides a concise and flexible means for "matching" strings of text, such as particular characters, words, or patterns of characters. Abbreviations for "regular expression" include "regex" and "regexp"...