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diff --git a/miniany/doc/lotabout.me_2016_Let-s-Build-a-C-Interpreter-0.txt b/miniany/doc/lotabout.me_2016_Let-s-Build-a-C-Interpreter-0.txt new file mode 100644 index 0000000..78b8c4f --- /dev/null +++ b/miniany/doc/lotabout.me_2016_Let-s-Build-a-C-Interpreter-0.txt @@ -0,0 +1,168 @@ + #[1]alternate + + [2]Home[3]Books[4]About + [5]C[6]compiler + 2016-02-06 + +Let's Build a C Compiler(0) -- Preface + + Table of Contents + 1. [7]1. Why Compiler Theory + 2. [8]2. Hard to understand, hard to implement? + 3. [9]3. Original intention is for self-practicing + 4. [10]4. Caution + 5. [11]5. References + + EDIT: Note that I've include the full tutorial in the project + [12]write-a-C-interpreter. Please check that instead. + + In "Let's Build a C Compiler" series, we will build a compiler from + scratch for C programming language. I hope you will get some + understanding of compiler construction by the end of this tutorial. At + the same time we will build a usable compiler of C though some syntaxes + are not supported. + + Note that it is actually an Interpreter and can interpret itself. I use + the word "compiler" because it is more attractive, but we did more than + that. Also this series is actually written in Chinese in the first + place, If you are confused by my English, please leave some comments. + + In this very first chapter there will not be any code. If you are those + that likes code instead of texts, please skip. I'll talk about the + intention of this series. + +Why Compiler Theory + + What is the most important courses in computer science? I would give + "Data Structure", "Algorithm" and "Compiler Theory". In my point of + view, understanding recursion is the first level for programmers, and + writing a compiler is the next one. + + (Of course, there exists a lot of excellent programmers that don't + write a compiler, but at least writing one is a big challenge) + + People used to say that you can write more efficient code if you know + how the compiler works. But who cares when the modern computers have + performance so high that we can hardly imagine before? Then why bother + with compiler theory? + + Because it is cool! + + OK, admit it, you are still reading mainly because you are curious how + far would I go with this tutorial. But be careful, it will go quite + far. + + No? You just want to know how to build a compiler? OK then... my + mistake. + +Hard to understand, hard to implement? + + I have always been in awe of compiler. So when I went to college and + they taught compiler theory, I was so enthusiastic! And then... then I + quit, because I could not understand a single part. + + Normally a course about compiler will cover: + 1. How to represent syntax (such as BNF, etc.) + 2. Lexer, with somewhat NFA(nondeterministic finite automata), + DFA(deterministic finite automata). + 3. Parser, such as recursive descent, LL(k), LALR, etc. + 4. Intermediate Languages. + 5. Code generation. + 6. Code optimization. + + I believe that most(98%) students will not care anything beyond + parser(at least in my school). And the most important thing is: we + still don't know how to build a compiler! Even after all these + theories. The main reason is that what "Compiler Theory" try to teach + is actually "how to build a parser generator", namely a tool that + consumes syntax grammar and generates compiler (such as lex/yacc). + + These theories try to taught us how to solve problems in a common way + automatically. That means once you master them, you are able to deal + with all kinds of grammars. They are indeed useful in industry. + Nevertheless they are too powerful and too complicate for students and + most programmers. You will be convinced if you read the source code of + lex/yacc (or flex/bison). + + The good news is, building a compiler is far simpler than you'd ever + imagined. I won't lie, it is not easy, but not that hard. + +Original intention is for self-practicing + + I saw [13]c4 on Github. It is a small C interpreter which is claimed to + be implemented by only 4 functions. The most amazing part is that it is + bootstrapping (that interpret itself). Also it is done with about 500 + lines! + + Existing tutorials is either very simple(such as implementing a simple + calculator) or using automation tools(such as flex/bison). c4 is + implemented all on its own. The bad thing is that it try to be minimal, + so the code is quite a mess, hard to understand. So I started a new + project that: + 1. implement a working C compiler(interpreter actually) + 2. Writing this tutorial to show how to do it. + + c4 is about 500 Lines, it took 1 week for me to re-write it, resulting + 1400 lines including comments. The project is hosted on Github: + [14]Write a C Interpreter + + Note: Almost all logic of this project is taken from c4. So the + original author(rswier) takes credit. + +Caution + + Two major problem I met when I working with this project are: + 1. boring, there will be codes that are almost identical. + 2. hard to debug. We don't have good test cases. On the other hand if + the output is wrong, I could only follow the generated code all by + myself to debug. + + So I hope you'll take out enough time and patience for studying, cause + I am sure that you will feel a great sense of accomplishment just like + I do. + +References + + 1. [15]Let's Build a Compiler: a very good tutorial of building a + compiler for fresh starters. + 2. [16]Lemon Parser Generator: the parser generator that is used in + SQLite. Good to read if you won't to understand compiler theory in + code. + + In the end, I am human with a general level, there will be inevitably + wrong with the articles and codes(also my English). Feel free to + correct me! + + Hope you enjoy it. + + Please enable JavaScript to view the [17]comments powered by Disqus. + [18]Blog comments powered by Disqus + +References + + Visible links: + 1. https://lotabout.me/atom.xml + 2. https://lotabout.me/ + 3. https://lotabout.me/books + 4. https://lotabout.me/about + 5. https://lotabout.me/tags/C/ + 6. https://lotabout.me/tags/compiler/ + 7. https://lotabout.me/2016/Let-s-Build-a-C-Interpreter-0/#why-compiler-theory + 8. https://lotabout.me/2016/Let-s-Build-a-C-Interpreter-0/#hard-to-understand-hard-to-implement + 9. https://lotabout.me/2016/Let-s-Build-a-C-Interpreter-0/#original-intention-is-for-self-practicing + 10. https://lotabout.me/2016/Let-s-Build-a-C-Interpreter-0/#caution + 11. https://lotabout.me/2016/Let-s-Build-a-C-Interpreter-0/#references + 12. https://github.com/lotabout/write-a-C-interpreter/tree/master/tutorial/en + 13. https://github.com/rswier/c4 + 14. https://github.com/lotabout/write-a-C-interpreter + 15. http://compilers.iecc.com/crenshaw/ + 16. http://www.hwaci.com/sw/lemon/ + 17. http://disqus.com/?ref_noscript + 18. http://disqus.com/ + + Hidden links: + 20. https://lotabout.me/2016/Let-s-Build-a-C-Interpreter-0/#why-compiler-theory + 21. https://lotabout.me/2016/Let-s-Build-a-C-Interpreter-0/#hard-to-understand-hard-to-implement + 22. https://lotabout.me/2016/Let-s-Build-a-C-Interpreter-0/#original-intention-is-for-self-practicing + 23. https://lotabout.me/2016/Let-s-Build-a-C-Interpreter-0/#caution + 24. https://lotabout.me/2016/Let-s-Build-a-C-Interpreter-0/#references |