Building a Compiler in JRuby - Chris Umbel at Jan 24th 2012 PittJUG meeting showing how you can create a language using JRuby tools to parse the language an emit JVM bytecode.

1. Building a Miserably
Fun Compiler in
JRuby.
Chris Umbel
@chrisumbel
http://www.chrisumbel.com
Sunday, January 29, 12

2. Agenda
Ruby/JRuby introduction
Talk background
Building a compiler
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3. Ruby
Dynamic, but strongly typed.
Object-oriented
metaprogrammable
Has multiple implementations (MRI,
IronRuby, Rubinius, JRuby)
Has functional features (Higher-order
functions, blocks)
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4. Ruby Examples
OO
Data Structures
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5. JRuby
Highly compatible Ruby implementation
Written in Java/runs on the JVM
Can consume arbitrary Java libraries
Favorable concurrency characteristics
to CRuby (no GIL)
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6. JRuby Examples
Java types
Using .jars
conventions
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7. Inspiration
Ian Dees @undees
JRubyConf 2011
JRuby, Not Just for Hard-Headed
Pragmatists Anymore
Author: Using JRuby: Bringing Ruby to
Java
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8. JRubyConf
Practical problem solving
Customers, Customers, Customers!
ROI
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9. Thnad
Just enough of a fictional
programming language to show how to
write a compiler
https://github.com/undees/thnad
Sort of JavaScript-ey
Allusion to the greatest of classical
literature
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10. What We’ll Build
Lisp-style S-expressions
Pure JRuby
Compiles to Java bytecode
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11. What We’ll Use
JRuby
Parslet
Kaspar Shiess
Parser in pure Ruby
Bitescript
Charles Nutter
JVM bytecode emitter for JRuby
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12. What it wont’ do
Conditionals
Non-parametric locally scoped
variables
OO
Provide Java library support,
standard or otherwise.
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13. What It’ll Do
Basic math
Functions
Standard output
Suck!!!
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14. sucklang
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15. Language Components
Simple Atoms (identifiers; literal
strings and integers)
Lists
Function calls
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16. sucklang Code Sample
(defun foo [x y]
(+ x y))
(println "result is " (foo 6 9))
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17. Parts
Parser
Transmogrifier
Compiler
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18. Step 1
Parser
Numbers
Basic list
Whitespace handling
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19. Step 2
Parser
Expressions
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20. Step 3
Parser
Identifiers
Atoms
Lists in lists
Operators are Identifiers
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21. Step 4
Parser
Strings
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22. Step 5
Parser
Vectors
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23. Step 6
Transmogrifier
AST
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24. Step 7: STOP!
javap - Java disassembler
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25. Step 8
bitescript example
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26. Step 9
compiler
java requires/imports
emitting of simple types
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27. Step 10
emitting of functions
+
println
defun
calls
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28. What It Did
Parsed S-expressions into an AST
Compiled AST to JVM bytecode
Sucked (a lot of assumptions)
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29. What We’ve Learned
Parslet
Bitescript
JVM innards
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30. Thank you!
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