The best language in the world
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The document describes the design and implementation of a simple virtual machine. It discusses representing code as an AST and traversing it using a stack-based virtual machine. Key points include: - Frames are used to represent the call stack, containing local variables and the current instruction pointer. - The AST is traversed recursively, with nodes pushing and popping values on the frame stack. - Basic operations like addition are implemented as callable objects that manipulate the frame. - The AST can then be compiled to bytecode with instructions like PUSHINT and CALL to run on the virtual machine. - Finally, the document proposes generating native code instead of bytecode to remove the overhead of interpretation.
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The best language in the world
- 1. The best language in the world @voiser david@seedtag.com
- 2. It’s a really good solution for some problems
- 3. You should have a clear idea of: N-ary trees, DFT Visitor[T] pattern Two kinds of VM: “JVM” vs “Virtualbox”
- 4. Frontend A simple language is actually quite complex VM Bytecode generator Type checkerAST Native Backend Optimizer Standard library Memory management AST transformations
- 5. DSL / General purpose? Functional? OO? Native / VM / JIT? Existing VM? My own VM?
- 6. Frontend My recommendation: Start here and make a simple VM VM Bytecode generator Type checkerAST Native Backend Optimizer Standard library Memory management AST transformations
- 8. a = 1 b = 2 c = a + b print(c)
- 11. NFile( NDef(a, NInt(1)) NDef(b, NInt(2)) NDef(c, NCall(+, NRef(a), NRef(b))) NCall(print, NRef(c))))
- 12. Dynamic typing Stack based machine AST traversal
- 13. Frame: Stack + Local variables + Previous frame
- 14. Frame: Stack + Local variables + Previous frame Stack representation: [s0, s1, s2]
- 15. Frame: Stack + Local variables + Previous frame Locals representation {a:x, b:y}
- 16. Frame: Stack + Local variables + Previous frame Frame representation: [...] {...}
- 17. Frame operations: frame.push(object) -> () frame.pop() -> object frame.setlocal(str, object) -> () frame.pushlocal(str) -> () frame.call() -> ()
- 18. Rule Zero: Functions are represented by objects
- 19. Rule One: Each function gets its parameters from the stack, in reverse parameter order, and pushes a single element when returning.
- 20. interface FrameCallable { void call(frame); }
- 21. class PrintFunction() implements FrameCallable { def call(frame) { o = frame.pop(); // by Rule Zero System.out.println(o); frame.push(new Null()); // by Rule One } }
- 22. class SumFunction() implements FrameCallable { def call(frame) { i2 = frame.pop(); // by Rule Zero i1 = frame.pop(); // by Rule Zero sum = new Integer(i1.i + i2.i); frame.push(sum); // by Rule One } }
- 23. The initial frame has a bunch of locals that represent the basic language functions
- 24. Frame getRootFrame() { rootFrame = new Frame() frame.setlocal(print, new PrintFunction()) frame.setlocal(+, new SumFunction()) frame }
- 26. Let’s define a traverse operation void traverse(frame, node) { ??? }
- 27. NInt(x) Rule: Basic data nodes are represented by runtime objects
- 31. NCall(a, params) frame2 = new frame() params.foreach{ p => traverse(frame, p) frame2.push(frame.pop()) } frame2.pushlocal(a) frame2.call() frame.push(frame2.pop())
- 55. NFile( NDef(a, NInt(1)) NDef(b, NInt(2)) NDef(c, NCall(+, NRef(a), NRef(b))) NCall(print, NRef(c)))) [Null] {} [], {print,+,a:Int(1),b:Int(2),c:Int(3)} “3” appears in the console...
- 58. def plus1(x) { x + 1 } print(plus1(9))
- 60. class AstFunction(nfn) implements FrameCallable { def call(frame) { nfn.args.reverse.each { p => frame.storelocal(p, frame.pop()) } traverse(frame, nfn.body) } }
- 65. if (condition) then (true branch) else (false branch)
- 66. NIf(c, t, f) traverse(frame, c) if is_true(frame.pop()) traverse(frame, t) else traverse(frame, f)
- 67. Dynamic typing Stack based machine Bytecode generation
- 71. NFile( NDef(a, NInt(1)) NDef(b, NInt(2)) NDef(c, NCall(+, NRef(a), NRef(b))) NCall(print, NRef(c)))) PUSHINT 1 STORELOCAL a PUSHINT 2 STORELOCAL b
- 72. NFile( NDef(a, NInt(1)) NDef(b, NInt(2)) NDef(c, NCall(+, NRef(a), NRef(b))) NCall(print, NRef(c)))) PUSHINT 1 STORELOCAL a PUSHINT 2 STORELOCAL b PUSHLOCAL a
- 73. NFile( NDef(a, NInt(1)) NDef(b, NInt(2)) NDef(c, NCall(+, NRef(a), NRef(b))) NCall(print, NRef(c)))) PUSHINT 1 STORELOCAL a PUSHINT 2 STORELOCAL b PUSHLOCAL a PUSHLOCAL b
- 74. NFile( NDef(a, NInt(1)) NDef(b, NInt(2)) NDef(c, NCall(+, NRef(a), NRef(b))) NCall(print, NRef(c)))) PUSHINT 1 STORELOCAL a PUSHINT 2 STORELOCAL b PUSHLOCAL a PUSHLOCAL b PUSHLOCAL + CALL
- 75. NFile( NDef(a, NInt(1)) NDef(b, NInt(2)) NDef(c, NCall(+, NRef(a), NRef(b))) NCall(print, NRef(c)))) PUSHINT 1 STORELOCAL a PUSHINT 2 STORELOCAL b PUSHLOCAL a PUSHLOCAL b PUSHLOCAL + CALL STORELOCAL c
- 76. NFile( NDef(a, NInt(1)) NDef(b, NInt(2)) NDef(c, NCall(+, NRef(a), NRef(b))) NCall(print, NRef(c)))) PUSHINT 1 STORELOCAL a PUSHINT 2 STORELOCAL b PUSHLOCAL a PUSHLOCAL b PUSHLOCAL + CALL STORELOCAL c PUSHLOCAL c
- 77. NFile( NDef(a, NInt(1)) NDef(b, NInt(2)) NDef(c, NCall(+, NRef(a), NRef(b))) NCall(print, NRef(c)))) PUSHINT 1 STORELOCAL a PUSHINT 2 STORELOCAL b PUSHLOCAL a PUSHLOCAL b PUSHLOCAL + CALL STORELOCAL c PUSHLOCAL c PUSHLOCAL print CALL
- 78. What if I… … create a native library with a bunch of functions like: integer_new() integer_sum() print(), etc.
- 79. What if I… … generate assembly instead of bytecodes
- 80. What if I… … compile the assembly and link it against my native library
- 82. BOOM!BOOM!Now with free memory leaks!
- 84. Frontend Optimizer Bytecode generator Type checkerAST Native Backend VM Standard library Memory management AST transformations antlr / lex / yacc / bison asm, ast, ... LLVMRicher language Type theory
- 85. Thank you!