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<h2>What is ANTLR?</h2>

<p><strong>ANTLR</strong> (ANother Tool for Language Recognition) is a
powerful parser generator for reading, processing, executing, or
translating structured text or binary files. It's widely used to build
languages, tools, and frameworks.  From a grammar, ANTLR generates a
parser that can build and walk parse trees.</p>

<div id="terence"><img src="images/terence.jpg" alt="terence" />
<strong>Terence Parr</strong> is a tech lead at Google and until 2022 was a professor of data science / computer science at Univ. of San Francisco. He is the maniac behind ANTLR and has been
working on language tools since 1989.<br><br><i>Check out Terence impersonating a machine learning droid: <a href="http://explained.ai">explained.ai</a></i>
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<div style="font: 15px 'DroidSansBold'; padding: 10px 0; margin: 0 0 5px; color: #ec312e;">Quick Start
</div>
<div style="font: 13px 'DroidSansBold'">To try ANTLR immediately, jump to the <i>new</i> <u><a href="http://lab.antlr.org/" style="color: #C00">ANTLR Lab</a></u>!</div><br>

<div style="font-size: 14px">
To install locally, use <a href="https://github.com/antlr/antlr4-tools">antlr4-tools</a>, which installs Java and ANTLR if needed and creates <tt>antlr4</tt> and <tt>antlr4-parse</tt> executables:<br><br>
<pre>
<span class="dollar">$</span> <span class="cmd">pip</span> install antlr4-tools
</pre>
<br>
(Windows must add <tt>..\LocalCache\local-packages\Python310\Scripts</tt> to the <tt>PATH</tt>). See the <a href="https://github.com/antlr/antlr4/blob/master/doc/getting-started.md">Getting Started</a> doc.  Paste the following grammar into file <tt>Expr.g4</tt> and, from that directory, run the <tt>antlr4-parse</tt> command. Hit control-D on Unix (or control-Z on Windows) to indicate end-of-input. A window showing the parse tree will appear.
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<pre style="font-size: 12px">
<span style="color: #871F7C;">grammar</span> <span style="color:black">Expr</span>;
<span style="color: #00079C;">prog</span>:   (<span style="color: #00079C;">expr</span> <span style="color: #498393;">NEWLINE</span>)* ;
<span style="color: #00079C;">expr</span>:   <span style="color: #00079C;">expr</span> ('*'|'/') <span style="color: #00079C;">expr</span>
    |   <span style="color: #00079C;">expr</span> ('+'|'-') <span style="color: #00079C;">expr</span>
    |   <span style="color: #498393;">INT</span>
    |   '(' <span style="color: #00079C;">expr</span> ')'
    ;
<span style="color: #498393;">NEWLINE</span> : [\r\n]+ ;
<span style="color: #498393;">INT</span>     : [0-9]+ ;
</pre>
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<pre>
<span class="dollar">$</span> <span class="cmd">antlr4-parse</span> Expr.g4 prog -gui
10+20*30
<i>^D</i>
<span class="dollar">$</span> <span class="cmd">antlr4</span> Expr.g4  # gen code
<span class="dollar">$</span> <span class="cmd">ls</span> ExprParser.java
ExprParser.java
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	<h2>Latest News</h2>
	
<a class="twitter-timeline" href="https://twitter.com/the_antlr_guy" data-widget-id="373882077285871616">Tweets by @the_antlr_guy</a>
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<h2><a href="testimonials.html">Testimonials</a></h2>	

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	<div class="testimonial">
Kudos. I'm actually really liking ANTLR! I have a pretty darn good
velocity with a rapid prototyping project I am doing in my Google 20%
time. For example, I just discovered a feature in rewrite rules that
does exactly what I need (referencing previous rule ASTs, p. 174 in
your book). It took me about 5 minutes to get this to work and remove
an ugly wart from my grammar. Hats off!
<strong>Guido van Rossum, Inventor of Python</strong>
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	<div class="testimonial">
ANTLR is an exceptionally powerful and flexible tool for parsing
formal languages. At Twitter, we use it exclusively for query parsing
in Twitter search. Our grammars are clean and concise, and the
generated code is efficient and stable. The <a href="http://pragprog.com/titles/tpantlr2/the-definitive-antlr-4-reference">book</a> is our go-to
reference for ANTLR v4 -- engaging writing, clear descriptions and
practical examples all in one place.
<strong>Samuel Luckenbill, Senior Manager of Search Infrastructure, Twitter, inc.</strong>
	</div>

	<div class="testimonial">
Just wanted to take the opportunity to say thanks. ANTLR is a BIG
improvement over yacc/lex, and your support for it most
commendable. Managed to get my tired old brain around it in a
day. Nice work!
<strong>Brad Cox, Inventor of Objective-C</strong>
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<h2>Resources</h2>	

<a href="http://pragprog.com/titles/tpantlr2/the-definitive-antlr-4-reference"><img src="images/tpantlr2.jpg"
width=110></a>
<a href="http://pragprog.com/titles/tpdsl/language-implementation-patterns"><img src="images/tpdsl.jpg"
width=110></a>

<br><br><a href="https://github.com/antlr/antlr4/blob/master/doc/getting-started.md">Getting started with ANTLR v4</a>

<br><br><a href="https://github.com/antlr/antlr4/blob/4.13.2/doc/index.md">ANTLR
Documentation</a>

<br><br><a href="/api">Runtime API Doc</a>
<br><br><a href="https://github.com/antlr/antlr4">Browse source tree (github)</a>

<br><br><a href="https://github.com/antlr/antlr4/blob/master/doc/faq/index.md">Frequently Asked Questions</a>


<br><br><a href="http://www.stringtemplate.org">StringTemplate template engine</a>

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