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Bootstrapping a Forth Interpreter from Handwritten 1KB Binary

4 points by eatonphil 5y ago

nineties 5y ago
This project is to bootstrap a language processor from a hand-written ELF binary. This is a hobby project and is not intended for any practical use, but constructing a language processor completely from scratch is a lot of fun. Please try running, reading and playing with the code! Bootstrapping proceeds as follows: 1. Implement a simple Forth interpreter (really) by handwriting ELF. 2. Grow it into a relatively expressive language through self-extension. Since writing a program in machine language by hand is a tough work, the first interpreter is designed to be very simple. Every built-in word is single-letter and the interpreter just repeats that reads a character, looks it up from the dictionary and executes it. Also there is no error checking. This is the actual code for the first interpreter, which is a 136-byte implementation of the interpreter followed by a built-in dictionary of 888 bytes. https://github.com/nineties/planckforth/blob/main/planck.xxd https://github.com/nineties/planckforth/blob/main/planck.xxd The first interpreter and language is so esoteric that, for example, the Hello World looks like this. $ ./planck kHtketkltkltkotk tkWtkotkrtkltkdtk!tk:k0-tQ bootstrap.fs self-extends this. After running bootstrap.fs, the Hello World program can be written like this $ ./planck < bootstrap.fs ." Hello World!" cr At the beginning of bootstrap.fs, you can only use one-letter words, so the code is difficult to read as shown below. $ head bootstrap.fs h@l@h@!h@C+h!k1k0-h@$k:k0-h@k1k0-+$h@C+h!ih@!h@C+h!kefh@!h@C+h!l! h@l@h@!h@C+h!k1k0-h@$k h@k1k0-+$h@C+h!ih@!h@C+h!kefh@!h@C+h!l! h@l@ h@!h@C+h! k1k0-h@$ k\h@k1k0-+$ h@C+h! i h@!h@C+h! kkf h@!h@C+h! kLf h@!h@C+h! k:k0- h@!h@C+h! k=f h@!h@C+h! kJf h@!h@C+h! However, at the end, you can write a normal Forth program as follows. In this way, the interpreter and the language are extended during the execution of the single script. $ tail bootstrap.fs next-arg dup argv @ ! included else ." Welcome to PlanckForth " version type ." [" runtime type ." ]" cr copyright ." Type 'bye' to exit." cr s" /dev/tty" included then ; execute Various functionalities like compile mode, immediate mode, control-flow structures, literals, variables, constants, file I/O, heap memory, etc. will be available after running bootstrap.fs. Also, the language and bootstrap.fs are designed to be as environment-independent as possible, so you can implement the runtime in other languages as well. As an example, I added an implementation of the runtime in C and Python 3. There is no space for detailed explanation here. So please read the following source code and comments. https://github.com/nineties/planckforth/blob/main/bootstrap.fs https://github.com/nineties/planckforth/blob/main/bootstrap.... Also, there is a commentary article in Japanese here. I hope you can read it with google translate. (I will write it in English if I have time. someday.) https://qiita.com/9_ties/items/349b2ed65b7cd8a7d580 https://qiita.com/9_ties/items/349b2ed65b7cd8a7d580 Feedbacks and pull requests such as runtime implementations in other languages are very welcome. Thank you for reading.

4 points by eatonphil 5y ago

This project is to bootstrap a language processor from a hand-written ELF binary. This is a hobby project and is not intended for any practical use, but constructing a language processor completely from scratch is a lot of fun. Please try running, reading and playing with the code! Bootstrapping proceeds as follows: 1. Implement a simple Forth interpreter (really) by handwriting ELF. 2. Grow it into a relatively expressive language through self-extension. Since writing a program in machine language by hand is a tough work, the first interpreter is designed to be very simple. Every built-in word is single-letter and the interpreter just repeats that reads a character, looks it up from the dictionary and executes it. Also there is no error checking. This is the actual code for the first interpreter, which is a 136-byte implementation of the interpreter followed by a built-in dictionary of 888 bytes. https://github.com/nineties/planckforth/blob/main/planck.xxd https://github.com/nineties/planckforth/blob/main/planck.xxd The first interpreter and language is so esoteric that, for example, the Hello World looks like this. $ ./planck kHtketkltkltkotk tkWtkotkrtkltkdtk!tk:k0-tQ bootstrap.fs self-extends this. After running bootstrap.fs, the Hello World program can be written like this $ ./planck < bootstrap.fs ." Hello World!" cr At the beginning of bootstrap.fs, you can only use one-letter words, so the code is difficult to read as shown below. $ head bootstrap.fs h@l@h@!h@C+h!k1k0-h@$k:k0-h@k1k0-+$h@C+h!ih@!h@C+h!kefh@!h@C+h!l! h@l@h@!h@C+h!k1k0-h@$k h@k1k0-+$h@C+h!ih@!h@C+h!kefh@!h@C+h!l! h@l@ h@!h@C+h! k1k0-h@$ k\h@k1k0-+$ h@C+h! i h@!h@C+h! kkf h@!h@C+h! kLf h@!h@C+h! k:k0- h@!h@C+h! k=f h@!h@C+h! kJf h@!h@C+h! However, at the end, you can write a normal Forth program as follows. In this way, the interpreter and the language are extended during the execution of the single script. $ tail bootstrap.fs next-arg dup argv @ ! included else ." Welcome to PlanckForth " version type ." [" runtime type ." ]" cr copyright ." Type 'bye' to exit." cr s" /dev/tty" included then ; execute Various functionalities like compile mode, immediate mode, control-flow structures, literals, variables, constants, file I/O, heap memory, etc. will be available after running bootstrap.fs. Also, the language and bootstrap.fs are designed to be as environment-independent as possible, so you can implement the runtime in other languages as well. As an example, I added an implementation of the runtime in C and Python 3. There is no space for detailed explanation here. So please read the following source code and comments. https://github.com/nineties/planckforth/blob/main/bootstrap.fs https://github.com/nineties/planckforth/blob/main/bootstrap.... Also, there is a commentary article in Japanese here. I hope you can read it with google translate. (I will write it in English if I have time. someday.) https://qiita.com/9_ties/items/349b2ed65b7cd8a7d580 https://qiita.com/9_ties/items/349b2ed65b7cd8a7d580 Feedbacks and pull requests such as runtime implementations in other languages are very welcome. Thank you for reading.