Let’s Create An Interpreter In Go

Go Conference 2017 Autumn

Transcript

1. Let’s Create An Interpreter In Go Go Conference 2017 Autumn
2. Self Introduce • Kenshi Kamata • @knsh14 (twitter, GitHub) • KLab inc. ◦ Unity3d Editor Extension ◦ Create Facebook Instant Game
3. What I did? • Read Writing An Interpreter In Go ◦ https://interpreterbook.com/ • Actually Create An Interpreter • Create An Interpreter in about 1400 lines！ ◦ Included test code, about 2500 lines
4. DEMO let x = 0; let array = [0, 10, 20, 30, 40]; array[1]; let fib = fn(x) { if(x == 0) { 0; } else { if (x == 1) { 1;} else { fib(x-1) + fib(x-2);}}}; let loop = fn(i, max, f) { if(i == max){return 0;} f(); loop(i +1, max, f);}; let p = fn() { puts(“hello world”);};
5. Why I did? • I want to create self-produced Language • Tried “Writing An Interpreter In C” book ◦ but it was so hard and gave up • I heard good book by Go is released! so I decided to try again.
6. Specification • Monkey Language • Integer, Boolean, String, Function • Array, Hash • Able to use if statement ◦ No For loop • No yacc, use self-implemented Lexer and Parser
7. How long Until Finished • About 1 month • some finished in one week • Most of people can finish within 1.5 month
8. Hard Part • Parser logic was hard • Pratt Parser • google 演算子順位法 in japanese
9. What I learned • Fun to make Language by myself! • Understand AST a little through Parser Chapter • Not Following Go Practice in Some part
10. Understand AST • Build AST in Parser Chapter • Wrote A tool to check cyclomatic complexity with AST in past but it was poor code • I must be able to write better code after reading Parser chapter
11. Not Following Go Practice • Return Error ASAP / Return Error type • Not good practice in Interpreter • Example Code in Monkey • Actually, go/parser has similar code • https://golang.org/src/go/parser/parser.go filter by “p.error”, you can see no handling error
12. Not following Go practice • Don’t want to stop processing • For user experience, Parse to End then show all error messages • append to error string list, so not need to handle error at the time
13. Finally • Great feeling to exec code on my own interpreter ◦ different feeling to playing my own game • Good for Japanese people ◦ Easy English ◦ Understand by English after Understanding by Code
14. Next is Your Turn!!