Implementing Languages (FluentConf)

Programming is hard. Making compilers is harder. Or so people think. The truth is that making a compiler is just a series of small steps, using regular language constructs. It's so easy, we'll make one in this talk.

Transcript

1. Implementing Languages
2. Thanks FluentConf
3. Thanks SilverStripe
4. I Am Not A Special Snowflake
5. Compilers Are Not Important
6. Great Books On The Subject
9. Why Is This Useful?
10. Why Is This Useful? ▸ Improving productivity ▸ Communicating in a common domain language ▸ Alternative computational models
11. Tools You Can Use
12. Tools You Can Use ▸ Compiler generators ▸ String manipulation and state machines
13. int minutes = 90;
14. Grammar
15. Grammar ▸ List of rules which define structure and syntax ▸ Each rule is called a lexeme
16. int minutes = 90; e ! type id = value | type id
17. Lexer
18. Lexer ▸ Breaks code string into tokens ▸ Lexer ignores nesting
19. e ! type id = value | type id ["type", "int"], ["id", "minutes"], ["assign", "="], ["value", "90"],
20. Parser
21. Parser ▸ Arranges tokens in a hierarchy ▸ Checks tokens for syntax errors
22. ["type", "int"], ["id", "minutes"], ["assign", "="], ["value", "90"], ["definition", [ "int", "minutes", "90", ]]
23. Abstract Syntax Tree
24. Abstract Syntax Tree ▸ Represents constructs in the compiler's language
25. ["definition", [ "int", "minutes", "90", ]] new Definition( "int", "minutes", "90", )
26. Interpreter
27. Interpreter ▸ Calculates immediate effect to context ▸ Always accepts and returns a context
28. new Definition( "int", "minutes", "90", ) let context = {}; for (let i = 0; i < objects.length; i++) { context = objects[i].applyTo(context); }
29. Compiler
30. Compiler ▸ Writes the AST to a new language ▸ Checks constructs for semantic errors in target language
31. Recap
32. int minutes = 90; e ! type id = value | type id
33. e ! type id = value | type id ["type", "int"], ["id", "minutes"], ["assign", "="], ["value", "90"],
34. ["type", "int"], ["id", "minutes"], ["assign", "="], ["value", "90"], ["definition", [ "int", "minutes", "90", ]]
35. ["definition", [ "int", "minutes", "90", ]] new Definition( "int", "minutes", "90", )
36. new Definition( "int", "minutes", "90", ) let context = {}; for (let i = 0; i < objects.length; i++) { context = objects[i].applyTo(context); }
37. Yay!
38. Parser Expression Grammar
39. Parser Expression Grammar ▸ Uses pattern matching to tokenise and organise lexemes ▸ Generates a reusable interpreter and/or compiler
40. { var context = {}; function __set(key, value) { context[key] = value; } function __get(key) { return context[key]; } }
41. start = expression* expression = _ definition _ / _ inspection _ _ "whitespace" = [ \t\r\n]*
42. definition "definition" = t:type _ i:id _ assign _ v:value _ terminal { __set(i, v); } / t:type _ i:id _ terminal { __set(i, null); }
43. type "type" = "int" id "identity" = letters:[a-z]+ { return letters.join(""); } assign "assign" = "=" value "value" = numbers:[0-9]+ { return parseInt(numbers.join(""), 10); } terminal "terminal" = ";"
44. inspection "inspection" = "inspect" _ i:id _ terminal { console.log(__get(i)); }
45. Thanks CONFERENCES.OREILLY.COM/FLUENT/JAVASCRIPT-HTML-US/PUBLIC/SCHEDULE/DETAIL/46342 @ASSERTCHRIS