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My bytecode VM Lox interpreter |
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2024-10-06 |
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Last edit: 2024-10-06 |
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The aim of this post is to describe the general operation of the program and so… |
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So I continued with “Crafting Interpreters” by Robert Nystrom after making … |
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This version is written in C, which means we have to write a lot of code oursel… |
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## Compiler |
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The primary purpose of our compiler is to generate a chunk of code in bytecode … |
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### Scanner |
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The token scanner is very classic, with only one thing to say: the function res… |
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### Parser |
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An interesting point to note is that the author chose not to use a syntax tree … |
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We also implemented a Vaughan Pratt's parser, in our case a “top-down operato… |
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```c |
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typedef enum { |
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PREC_NONE, |
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PREC_ASSIGNMENT, // = |
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PREC_OR, // or |
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PREC_AND, // and |
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PREC_EQUALITY, // == != |
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PREC_COMPARISON, // < > <= >= |
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PREC_TERM, // + - |
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PREC_FACTOR, // * / |
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PREC_UNARY, // ! - |
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PREC_CALL, // . () |
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PREC_PRIMARY |
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} Precedence; |
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``` |
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This precedence is simply used to control the parsing of expressions. A rule wi… |
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## Bytecode |
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To manage conditions, we emit `OP_JUMP` operation code for conditions. If a con… |
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In my implementation, all immediate values are encoded on 8 bits, with the exce… |
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## Virtual Machine |
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The VM is centered on a stack where we push operands, local variables, etc.. |
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Everything at runtime is managed by callframes, even the top-level code is embe… |
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## Example |
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Here is a simple Lox example that can be evaluated by my interpreter. |
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```text |
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fun fib(n) { |
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if (n < 2) { |
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return n; |
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} |
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return fib(n - 2) + fib(n - 1); |
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} |
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print fib(10); |
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``` |
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## Links |
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https://github.com/theobori/lox-virtual-machine |
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