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- <title>Kaleidoscope: The basic language, with its lexer</title>
+ <title>Kaleidoscope: Tutorial Introduction and the Lexer</title>
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<meta name="author" content="Chris Lattner">
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-<div class="doc_title">Kaleidoscope: The basic language, with its lexer</div>
+<div class="doc_title">Kaleidoscope: Tutorial Introduction and the Lexer</div>
<ul>
<li><a href="index.html">Up to Tutorial Index</a></li>
<div class="doc_text">
<p>Welcome to the "Implementing a language with LLVM" tutorial. This tutorial
-will run the through implementation of a simple language, showing how fun and
+runs through the implementation of a simple language, showing how fun and
easy it can be. This tutorial will get you up and started as well as help to
-build a framework you can extend to other languages. You can also use this
-tutorial to help you start playing with other LLVM specific things.
+build a framework you can extend to other languages, allowing you to use this
+as a way to start playing with other LLVM specific things.
</p>
+<p>
+The goal of this tutorial is to progressively unveil our language, describing
+how it is built up over time. This will let us cover a fairly broad range of
+language design and LLVM-specific usage issues, showing and explaining the code
+for it all along the way, without overwhelming you with tons of details up
+front.</p>
+
+<p>It is useful to point out ahead of time that this tutorial is really about
+teaching compiler techniques and LLVM specifically, <em>not</em> about teaching
+modern and sane software engineering principles. In practice, this means that
+we'll take a number of shortcuts to simplify the exposition. For example, the
+code leaks memory, uses global variables all over the place, doesn't use nice
+design patterns like visitors, etc... but it is very simple. If you dig in and
+use the code as a basis for future projects, fixing these deficiencies shouldn't
+be hard.</p>
+
+<p>I've tried to put this tutorial together in a way that makes chapters easy to
+skip over if you are already familiar or are uninterested with various pieces.
+The structure of the tutorial is:
+</p>
+
+<ul>
+<li><b><a href="#language">Chapter #1</a>: Introduction to the Kaleidoscope
+language, and the definition of its Lexer</b> - This shows where we are going
+and the basic functionality that we want it to do. In order to make this
+tutorial maximally understandable and hackable, we choose to implement
+everything in C++ instead of using lexer and parser generators. LLVM obviously
+works just fine with such tools, feel free to use one if you prefer.</li>
+<li><b><a href="LangImpl2.html">Chapter #2</a>: Implementing a Parser and
+AST</b> - With the lexer in place, we can talk about parsing techniques and
+basic AST construction. This tutorial describes recursive descent parsing and
+operator precedence parsing. Nothing in Chapters 1 or 2 is LLVM-specific,
+the code doesn't even link in LLVM at this point. :)</li>
+<li><b><a href="LangImpl3.html">Chapter #3</a>: Code generation to LLVM IR</b> -
+With the AST ready, we can show off how easy generation of LLVM IR really
+is.</li>
+<li><b><a href="LangImpl4.html">Chapter #4</a>: Adding JIT and Optimizer
+Support</b> - Because a lot of people are interested in using LLVM as a JIT,
+we'll dive right into it and show you the 3 lines it takes to add JIT support.
+LLVM is also useful in many other ways, but this is one simple and "sexy" way
+that shows off its power. :)</li>
+<li><b><a href="LangImpl5.html">Chapter #5</a>: Extending the Language: Control
+Flow</b> - With the language up and running, we show how to extend it with
+control flow operations (if/then/else and a for loop). This gives us a chance
+to talk about simple SSA construction and control flow.</li>
+<li><b><a href="LangImpl6.html">Chapter #6</a>: Extending the Language:
+User-defined Operators</b> - This is a silly but fun chapter that talks about
+extending the language to let the user program define their own arbitrary
+unary and binary operators (with assignable precedence!). This lets us build a
+significant piece of the "language" as library routines.</li>
+<li><b><a href="LangImpl7.html">Chapter #7</a>: Extending the Language: Mutable
+Variables</b> - This chapter talks about adding user-defined local variables
+along with variable assignment operator. The interesting part about this is how
+easy and trivial it is to construct SSA form in LLVM (no, LLVM does <em>not</em>
+require your front-end to construct SSA form!).</li>
+<li><b><a href="LangImpl8.html">Chapter #8</a>: Conclusion and other useful LLVM
+tidbits</b> - This chapter wraps up the series by talking about potential
+ways to extend the language, but also includes a bunch of pointers to info about
+"special topics" like adding garbage collection support, exceptions, debugging,
+support for "spaghetti stacks", and a bunch of other tips and tricks.</li>
+
+</ul>
+
+<p>By the end of the tutorial, we'll have written about 700 lines of
+non-comment, non-blank lines of code. With this small amount of code, we'll
+have built up a very reasonable compiler for a non-trivial language including
+a hand-written lexer, parser, AST, as well as code generation support with a JIT
+compiler. While other systems may have interesting "hello world" tutorials,
+I think the breadth of this tutorial is a great testament to the strengths of
+LLVM and why you should consider it if you're interested in language or compiler
+design.</p>
+
+<p>A note about this tutorial: we expect you to extend the language and play
+with it on your own. Take the code and go crazy hacking away at it. It can be
+a lot of fun to play with languages! In any case, lets get into the code!</p>
+
</div>
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</div>
-<p>In the first incarnation of the language, we will only support basic
-arithmetic: if/then/else will be added in a future installment. Another
-interesting aspect of the first implementation is that it is a completely
-functional language, which does not allow you to have side-effects, etc. We
-will eventually add side effects for those who prefer them.</p>
-
-<p>In order to make this tutorial
-maximally understandable and hackable, we choose to implement everything in C++
-instead of using lexer and parser generators. LLVM obviously works just fine
-with such tools, and making use of them doesn't impact the overall design.</p>
-
-<p>A note about this tutorial: we expect you to extend the language and play
-with it on your own. Take the code and go crazy hacking away at it. It can be
-a lot of fun to play with languages!</p>
+<p>A more interesting example is included in Chapter 6 where we show the code
+used to <a href="LangImpl6.html#example">implement a Mandelbrot Set viewer</a>
+in Kaleidoscope.</p>
</div>
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