Trolls of 2013ryan/presentations/2013_MWRC... · 2013-04-08 · MWRC 2013, Salt Lake City, UT...

MWRC 2013, Salt Lake City, UT

Ryan Davis, Seattle.rbTrolls of 2013

Trolls of 2013


Ryan Davis, Seattle.rbTrolls of 2013

• Followup of my talk, “Occupy Ruby: Why We Need to Moderate the 1%”

• 130 Slides in 30 minutes. 4.3 spm

• I must go quickly, so please hold questions.

• Ummm... no.

Setting Expectations


Ryan Davis, Seattle.rbLet’s Write an Interpreter!

Let’s Wr!e an Interpreter!



Setting Expectations

• 160 Slides in 30 minutes. 5.3 spm.

• Boatloads of content. Almost all code.

• I was asked to “Hurt Brains”.

• TODO



Expanded to 45 minutes?!?



Added15 minutes of kittens

to the end



OMG WHY?!?



BecauseI’m a pervert!



Wa!… No!



Because we can!



"e “Uby”Interpreter



Branching Logic:if/else/elsif

if condition then true_codeelse false_codeend



Loops: whilewhile condition codeend



Local Variablesmeaning = 42pi = 3



Functionsdef fib n if n <= 2 then 1 else fib(n-2) + fib(n-1) endend



Functions

recursive function calls

local variables

“primitive” function callsdef fib n if n <= 2 then 1 else fib(n-2) + fib(n-1) endend



Uby Roadmap

Variables Conditionals

Runtime

Environment

Functions

Parser

Loops



Parsing: ruby_parser



ConditionalsLoops

Runtime

Environment

Functions

Parser

Variables



RubyParser.new.parse " def fib n if n <= 2 then 1 else fib(n-2) + fib(n-1) end end"



:defn

:fib

:args:n

:if

:call

:lvar :n

:<

:lit 2

:lit 1

:call

:call

nil

:fib

:call

:lvar :n

:-

:lit 2:+

:call nil :fib

:call

:lvar :n

:-

:lit 1



:defn

:fib

:args

:n

:if

:call

:lvar :n

:<

:lit 2

:lit 1

:call

:call

nil

:fib

:call

:lvar :n

:-

:lit 2:+

:call nil :fib

:call

:lvar :n

:-

:lit 1



else

:call nil :fib

:call

:lvar :n

:-

:lit 1

:call nil :fib

:call

:lvar :n

:-

:lit 2

:call :+

condition

:call

:lvar :n

:<

:lit 2

:defn

:fib :args

:n

:if

then

:lit 1



s(:defn, :fib, s(:args, :n), s(:if, s(:call, s(:lvar, :n), :<=, s(:lit, 2)), s(:lit, 1), s(:call, s(:call, nil, :fib, s(:call, s(:lvar, :n), :-, s(:lit, 2))), :+, s(:call, nil, :fib, s(:call, s(:lvar, :n), :-, s(:lit, 1))))))



S-Expression Vocabulary

s(:call, s(:lit, 3), :+, s(:lit, 4))

Sexp Sub-sexps

Rest(cdr)

Head/Type(car)



All for free using ruby_parser



OK…No more talk about

parsing.



Further study on parsers:

Michael Jackson’sParsing Expressions in Ruby

MWRC 2011http://www.confreaks.com/videos/582



Interpre#ng via sexp_processor



ConditionalsLoops

Environment

Variables

Functions

Parser

Runtime



How to get 7 from 3+4?

73 + 4 ??????



Start with the source

3 + 4



Parse it

3 + 4s(:call, s(:lit, 3), :+, s(:lit, 4))



s(:call, s(:lit, 3), :+, s(:lit, 4))

Then process by type

3 + 4

process_call

process_lit



s(:call, s(:lit, 3), :+, s(:lit, 4))

First with the inner values

3 + 4

process_lit



s(:call, 3, :+, s(:lit, 4))


3 + 4

process_lit



s(:call, 3, :+, 4)


3 + 4



s(:call, 3, :+, 4)

then with the outer

3 + 4

process_call



proc { |a, b| a + b }[3, 4]

then with the outer

3 + 4



proc { |a, b| a + b }[3, 4]

resulting in a final value

3 + 4 7



SexpProcessorclass UbyInterpreter def process_lit s s.last endend s(:lit, 3)

3



Test Dr$en Interpreters



Loops Conditionals

Runtime

Environment

Functions

Parser

Test

Dri

ven

Variables



Unit Testsdef test_sanity val = lang.eval("3 + 4") assert_equal 7, valend



Unit TestsInput Source

Expected Value

def test_sanity val = lang.eval("3 + 4") assert_equal 7, valend



Premature Refactoring

Input SourceExpected Value

def assert_eval exp, src assert_equal exp, lang.eval(src)end

def test_sanity assert_eval 7, "3 + 4"end



San% Test:3 + 4



ConditionalsLoops

Environment

Functions

Parser

Test

Dri

ven

Runtime

Variables



Test Infrastructureclass TestUbyInterpreter < MiniTest::Unit::TestCase attr_accessor :int

def setup self.int = UbyInterpreter.new end

def assert_eval exp, src, msg = nil assert_equal exp, int.eval(src), msg endend



Our First Test:class TestUbyInterpreter < MiniTest::Unit::TestCase attr_accessor :int


def assert_eval exp, src assert_equal exp, ri.eval(src) end

def test_sanity assert_eval 3, "3" assert_eval 7, "3 + 4" endend

Old Code

New Code



Our First Test:class TestUbyInterpreter < MiniTest::Unit::TestCase

# ...

def test_sanity assert_eval 3, "3" assert_eval 7, "3 + 4" endend

Old Code

New Code



Our first error:# Running tests:

E

Finished tests in 0.000364s, 2747.2527 tests/s, 0.0000 assertions/s.

1) Error:TestUbyInterpreter#test_sanity:NameError: uninitialized constant TestUbyInterpreter::UbyInterpreter ./test/test_ruby_interpreter.rb:11:in `setup'



Define the constantclass UbyInterpreter < SexpInterpreter VERSION = "1.0.0"end



Wash, rinse…# Running tests:

E


1) Error:TestUbyInterpreter#test_sanity:NoMethodError: private method `eval' called for #<UbyInterpreter:0x105be17d8> ./test/test_ruby_interpreter.rb:15:in `assert_eval' ./test/test_ruby_interpreter.rb:19:in `test_sanity'



Implement eval & parseclass UbyInterpreter < SexpInterpreter # ... attr_accessor :parser

def initialize super

self.parser = Ruby19Parser.new end

def eval src process parse src end

def parse src self.parser.process src endend



Finally!# Running tests:

E


1) Error:TestUbyInterpreter#test_sanity:UnknownNodeError: Bug! Unknown node-type :lit to UbyInterpreter ./lib/ruby_interpreter.rb:17:in `eval' ./test/test_ruby_interpreter.rb:15:in `assert_eval' ./test/test_ruby_interpreter.rb:19:in `test_sanity'



Implement process_litclass UbyInterpreter < SexpInterpreter

# ...

def process_lit s s.last endend



Tada! Second Assertion! 1) Error:TestUbyInterpreter#test_sanity:UnknownNodeError: Bug! Unknown node-type :call to UbyInterpreter ./lib/ruby_interpreter.rb:17:in `eval' ./test/test_ruby_interpreter.rb:15:in `assert_eval' ./test/test_ruby_interpreter.rb:20:in `test_sanity'



Define :call genericallyclass UbyInterpreter < SexpInterpreter

# ...

def process_call s raise "Boom: #{s.inspect}" endend



See sub-sexps 1) Error:TestUbyInterpreter#test_sanity:RuntimeError: Boom: s(:call, s(:lit, 3), :+, s(:lit, 4)) ./lib/ruby_interpreter.rb:35:in `process_call' ./lib/ruby_interpreter.rb:19:in `eval' ./test/test_ruby_interpreter.rb:17:in `assert_eval' ./test/test_ruby_interpreter.rb:22:in `test_sanity'



Unpack sub-sexpsclass UbyInterpreter < SexpInterpreter

# ...

def process_call s _, recv, msg, *args = s

raise "Boom: #{recv}, #{msg}, #{args.inspect}" endend



Unpacked sub-sexps 1) Error:TestUbyInterpreter#test_sanity:RuntimeError: Boom: s(:lit, 3), +, [s(:lit, 4)] ./lib/ruby_interpreter.rb:31:in `process_call'



Process sub-sexpsclass UbyInterpreter < SexpInterpreter def process_call s _, recv, msg, *args = s

recv = process recv args.map! { |sub| process sub }

raise "Boom: #{recv}, #{msg}, #{args.inspect}" endend



Processed Values 1) Error:TestUbyInterpreter#test_sanity:RuntimeError: Boom: 3, +, [4] ./lib/ruby_interpreter.rb:43:in `process_call'



Cheat: Send to Rubyclass UbyInterpreter < SexpInterpreter def process_call s _, recv, msg, *args = s


recv.send(msg, *args) # big ol' hack… endend



Sanity!# Running tests:

.


1 tests, 2 assertions, 0 failures, 0 errors, 0 skips


Ryan Davis, Seattle.rbLet’s Write an Interpreter!class UbyInterpreter < SexpInterpreter VERSION = "1.0.0"

attr_accessor :parser

def initialize super self.parser = Ruby19Parser.new end


def parse src self.parser.process src end

def process_lit s s.last end




Yay!

Overblown

Calculator!



Cond!ionals&

Truthiness



Loops

Runtime

Environment

Variables

Functions

Parser

Test

Dri

ven

Conditionals



Add :if testsclass TestUbyInterpreter < MiniTest::Unit::TestCase # ...

def test_if assert_eval 42, "if true then 42 else 24 end" end

def test_if_falsey assert_eval 24, "if nil then 42 else 24 end" assert_eval 24, "if false then 42 else 24 end" endend



Unknown :if 1) Error:TestUbyInterpreter#test_if:UnknownNodeError: Bug! Unknown node-type :if to UbyInterpreter ./lib/ruby_interpreter.rb:17:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:34:in `test_if'

2) Error:TestUbyInterpreter#test_if_falsey:UnknownNodeError: Bug! Unknown node-type :if to UbyInterpreter ./lib/ruby_interpreter.rb:17:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:38:in `test_if_falsey'




Define :if genericallyclass UbyInterpreter < SexpInterpreter # ...

def process_if s raise "Boom: #{s.inspect}" endend



See sub-sexps 1) Error:TestUbyInterpreter#test_if:RuntimeError: Boom: s(:if, s(:true), s(:lit, 42), s(:lit, 24)) ./lib/ruby_interpreter.rb:38:in `process_if' ... ./lib/ruby_interpreter.rb:17:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:34:in `test_if'

2) Error:TestUbyInterpreter#test_if_falsey:RuntimeError: Boom: s(:if, s(:nil), s(:lit, 42), s(:lit, 24)) ./lib/ruby_interpreter.rb:38:in `process_if' ... ./lib/ruby_interpreter.rb:17:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:38:in `test_if_falsey'



Process sub-sexpsclass UbyInterpreter < SexpInterpreter # ...

def process_if s _, c, t, f = s

c = process c

if c then process t else process f end endend

Why evaluate c before t &

f?

if true then puts "happy"else system "rm -rf /"end



Sub-sexps fail 1) Error:TestUbyInterpreter#test_if:UnknownNodeError: Bug! Unknown node-type :true to UbyInterpreter ./lib/ruby_interpreter.rb:40:in `process_if' ./lib/ruby_interpreter.rb:17:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:34:in `test_if'

2) Error:TestUbyInterpreter#test_if_falsey:UnknownNodeError: Bug! Unknown node-type :nil to UbyInterpreter ./lib/ruby_interpreter.rb:40:in `process_if' ./lib/ruby_interpreter.rb:17:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:38:in `test_if_falsey'



Define :nil and :trueclass UbyInterpreter < SexpInterpreter # ...

def process_nil s nil end

def process_true s true endend



Third failure 1) Error:TestUbyInterpreter#test_if_falsey:UnknownNodeError: Bug! Unknown node-type :false to UbyInterpreter ./lib/ruby_interpreter.rb:40:in `process_if' ./lib/ruby_interpreter.rb:17:in `eval' ./test/test_ruby_interpreter.rb:15:in `assert_eval' ./test/test_ruby_interpreter.rb:39:in `test_if_falsey'



Define :falseclass UbyInterpreter < SexpInterpreter # ...

def process_false s false endend



Voilà!# Running tests:

...





Test Driven Process

Processsub-sexps

Tests Pass

Add afailing test

Errornode-type

Add genericnode-type

Failure sub-sexpcomponents



Yes, development this fast…

with autotest.



Brain Hurt Yet?



Good



Wait till I get going!

Where was I?



Local Variables



Loops Conditionals

Runtime

Functions

Parser

Test

Dri

ven

Variables

Environment



Local Variables!class TestUbyInterpreter < MiniTest::Unit::TestCase # ...

def test_lvar assert_eval 42, "x = 42; x" endend



Block?!? 1) Error:TestUbyInterpreter#test_lvar:UnknownNodeError: Bug! Unknown node-type :block to UbyInterpreter ./lib/ruby_interpreter.rb:17:in `eval' ./test/test_ruby_interpreter.rb:15:in `assert_eval' ./test/test_ruby_interpreter.rb:24:in `test_lvar'



Define :blockclass UbyInterpreter < SexpInterpreter # ...

def process_block s raise "Boom: #{s.inspect}" endend



Ohhh… 1) Error:TestUbyInterpreter#test_lvar:RuntimeError: Boom: s(:block, s(:lasgn, :x, s(:lit, 42)), s(:lvar, :x)) ./lib/ruby_interpreter.rb:25:in `process_block' ./lib/ruby_interpreter.rb:17:in `eval' ./test/test_ruby_interpreter.rb:15:in `assert_eval' ./test/test_ruby_interpreter.rb:24:in `test_lvar'



Process all sub-sexpsclass UbyInterpreter < SexpInterpreter # ...

def process_block s result = nil s.rest.each do |sub| result = process sub end result endend



:lasgn is undefined 1) Error:TestUbyInterpreter#test_lvar:UnknownNodeError: Bug! Unknown node-type :lasgn to UbyInterpreter ./lib/ruby_interpreter.rb:27:in `process_block' ./lib/ruby_interpreter.rb:26:in èach' ./lib/ruby_interpreter.rb:26:in `process_block' ./lib/ruby_interpreter.rb:17:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:24:in `test_lvar'



Define :lasgnclass UbyInterpreter < SexpInterpreter # ...

def process_lasgn s raise "Boom: #{s.inspect}" endend



Looks like name/value 1) Error:TestUbyInterpreter#test_lvar:RuntimeError: Boom: s(:lasgn, :x, s(:lit, 42)) ./lib/ruby_interpreter.rb:58:in `process_lasgn' ./lib/ruby_interpreter.rb:27:in `process_block' ./lib/ruby_interpreter.rb:26:in èach' ./lib/ruby_interpreter.rb:26:in `process_block' ./lib/ruby_interpreter.rb:17:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:24:in `test_lvar'



Add a stupid tableclass UbyInterpreter < SexpInterpreter # ...

attr_accessor :env

def initialize # ... self.env = {} # omg this is horrible end

def process_lasgn s _, n, v = s

self.env[n] = process v endend

EnvironmentEnvironment

x 42



Now we need to read 1) Error:TestUbyInterpreter#test_lvar:UnknownNodeError: Bug! Unknown node-type :lvar to UbyInterpreter ./lib/ruby_interpreter.rb:29:in `process_block' ./lib/ruby_interpreter.rb:28:in èach' ./lib/ruby_interpreter.rb:28:in `process_block' ./lib/ruby_interpreter.rb:19:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:24:in `test_lvar'



Access the tableclass UbyInterpreter < SexpInterpreter # ...

def process_lvar s _, name = s

self.env[name] endend



Voilà# Running tests:

....





Just wait…



It gets “better”



Fun&ions



Conditionals

Runtime

Environment

Variables

Parser

Test

Dri

ven

Loops

Functions



Add :defn Testclass TestUbyInterpreter < MiniTest::Unit::TestCase # ...

def test_defn assert_eval nil, <<-EOM def double n 2 * n end EOM

assert_eval 42, "double(21)" endend



Unknown :defn 1) Error:TestUbyInterpreter#test_defn:UnknownNodeError: Bug! Unknown node-type :defn to UbyInterpreter ./lib/ruby_interpreter.rb:19:in `eval' ./test/test_ruby_interpreter.rb:17:in `assert_eval' ./test/test_ruby_interpreter.rb:45:in `test_defn'



Generic :defnclass UbyInterpreter < SexpInterpreter # ...

def process_defn s raise "Boom: #{s.inspect}" endend



Examine sub-sexps 1) Error:TestUbyInterpreter#test_defn:RuntimeError: Boom: s(:defn, :double, s(:args, :n), s(:call, s(:lit, 2), :*, s(:lvar, :n))) ./lib/ruby_interpreter.rb:44:in `process_defn' ./lib/ruby_interpreter.rb:19:in `eval' ./test/test_ruby_interpreter.rb:17:in `assert_eval' ./test/test_ruby_interpreter.rb:45:in `test_defn'



Unpack & Storeclass UbyInterpreter < SexpInterpreter # ...

def process_defn s _, name, args, *body = s

self.env[name] = [args, body]

nil endend


n 8

life 42

pi 3

double

[ s(:args, :n),

[s(:call, s(:lit, 2), :*, s(:lvar, :n))]]



What’s up with :call? 1) Error:TestUbyInterpreter#test_defn:NoMethodError: undefined method `double' for nil:NilClass ./lib/ruby_interpreter.rb:40:in `send' ./lib/ruby_interpreter.rb:40:in `process_call' ./lib/ruby_interpreter.rb:19:in `eval' ./test/test_ruby_interpreter.rb:17:in `assert_eval' ./test/test_ruby_interpreter.rb:54:in `test_defn'



No NilClass#doubleclass UbyInterpreter < SexpInterpreter # ...






Isolate the Problemclass UbyInterpreter < SexpInterpreter # ...



if recv then recv.send(msg, *args) # less of a hack else raise "argh" end endend



Error, Isolated 1) Error:TestUbyInterpreter#test_defn:RuntimeError: argh ./lib/ruby_interpreter.rb:43:in `process_call' ./lib/ruby_interpreter.rb:19:in `eval' ./test/test_ruby_interpreter.rb:17:in `assert_eval' ./test/test_ruby_interpreter.rb:54:in `test_defn'



Set vars & run the codeclass UbyInterpreter < SexpInterpreter # ...



if recv then recv.send(msg, *args) # less of a hack else decls, body = self.env[msg]

decls.rest.zip(args).each do |name, val| self.env[name] = val end

process_block s(:block, *body) end endend



args... decls... zip bwuh?




n 21

life 42

pi 3

double

[ s(:args, :n),

s(:call, s(:lit, 2), :*, s(:lvar, :n))]


n 8

life 42

pi 3

double

[ s(:args, :n),

s(:call, s(:lit, 2), :*, s(:lvar, :n))]

s(:call, nil, :double, s(:lit, 21))

decls.rest.zip(args).each do |k, v| self.env[k] = vend

[:n].zip([21]).each do |k, v| self.env[k] = vend

self.env[:n] = 21

decls

args



Voilà!# Running tests:

.....





“Getting to green just means you don’t have enough

tests.”– Kent Beck



Fibonacci



Conditionals

Runtime

Parser

Test

Dri

ven

Environment

Loops

Functions

Variables



Finally Freakin’ Fibonacci!class TestUbyInterpreter < MiniTest::Unit::TestCase # ...

def test_fib assert_eval nil, <<-END def fib n if n <= 2 then 1 else fib(n-2) + fib(n-1) end end END

assert_eval 8, "fib(6)" endend



Whoa… it ran… but failed 1) Failure:TestUbyInterpreter#test_fib [./test/test_ruby_interpreter.rb:71]:Expected: 8 Actual: 3





n 4

life 42

pi 3

fib

[ s(:args, :n),

s(:if, ...)]


n 6

life 42

pi 3

fib

[ s(:args, :n),

s(:if, ...)]


n 8

life 42

pi 3

fib

[ s(:args, :n),

s(:if, ...)]

That stupid Table?Yeah...

def fib n if n <= 2 then 1 else fib(n-2) + fib(n-1) endendn = 8; fib(6)n = 6; fib(4) + fib(5)n = 4; ... and so on...



[ s(:args, :n),

s(:if, ...)]

fib

3pi

42life

n 8

[ s(:args, :n),

s(:if, ...)]

fib

3pi

42life

n 5

[ s(:args, :n),

s(:if, ...)]

fib

3pi

42life

n 3

[ s(:args, :n),

s(:if, ...)]

fib

3pi

42life

n 1

Wanted: Stacked Hashn 1

n 3

n 5

[ s(:args, :n),

s(:if, ...)]

fib

3pi

42life

n 8

fib(1)

fib(3)

fib(5)

original

but acts like:



6z

5y

4x

2b

3c

42x

1a

z 6

y 5

x 42

3c

2b

1a

Environment Classenv[:x] == ?

env[:x] = 42

all:

scope:

scope:

scope:


Ryan Davis, Seattle.rbLet’s Write an Interpreter!class UbyInterpreter < SexpInterpreter # ...

class Environment def [] k self.all[k] end

def []= k, v @env.last[k] = v end

def all @env.inject(&:merge) end

def scope @env.push({})

yield ensure @env.pop end

def initialize @env = [{}] end endend

Writes to top layer only

Reads from everything

Flattened. Newest wins

Automatic layering



Replace stupid tableclass UbyInterpreter < SexpInterpreter # ...

def initialize # ... self.env = Environment.new end

# ...end



Scope every callclass UbyInterpreter < SexpInterpreter # ...



if recv then recv.send(msg, *args) # less of a hack else self.env.scope do decls.rest.zip(args).each do |name, val| self.env[name] = val end

process_block s(:block, *body) end end endend



Finally# Running tests:

......





While Loops



Runtime

Environment

Variables

Functions

Parser

Test

Dri

ven

ConditionalsLoops



Refactor Fibonnaciclass TestUbyInterpreter < MiniTest::Unit::TestCase # ...

def define_fib assert_eval nil, <<-END def fib n if n <= 2 then 1 else fib(n-2) + fib(n-1) end end END endend



Add :while testsclass TestUbyInterpreter < MiniTest::Unit::TestCase # ...

def test_while_sum_of_fibs define_fib

assert_eval 1+1+2+3+5+8+13+21+34+55, <<-EOM n = 1 sum = 0 while n <= 10 sum += fib(n) n += 1 end sum EOM endend



Unknown :while 1) Error:TestUbyInterpreter#test_while_fib:UnknownNodeError: Bug! Unknown node-type :while to UbyInterpreter ./lib/ruby_interpreter.rb:29:in `process_block' ./lib/ruby_interpreter.rb:28:in èach' ./lib/ruby_interpreter.rb:28:in `process_block' ./lib/ruby_interpreter.rb:19:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:86:in `test_while_fib'



Define :while genericallyclass UbyInterpreter < SexpInterpreter # ...

def process_while s raise "Boom: #{s.inspect} endend



See sub-sexps 1) Error:TestUbyInterpreter#test_while:RuntimeError: Boom: s(:while, s(:call, s(:lvar, :n), :<, s(:lit, 41)), s(:lasgn, :n, s(:call, s(:lvar, :n), :+, s(:lit, 1))), true) ./lib/ruby_interpreter.rb:104:in `process_while' ./lib/ruby_interpreter.rb:29:in `process_block' ./lib/ruby_interpreter.rb:28:in èach' ./lib/ruby_interpreter.rb:28:in `process_block' ./lib/ruby_interpreter.rb:19:in èval' ./test/test_ruby_interpreter.rb:15:in àssert_eval' ./test/test_ruby_interpreter.rb:62:in `test_while'



Define :whileclass UbyInterpreter < SexpInterpreter # ...

def process_while s _, cond, *body = s body.pop # pre vs post condition -- ignore for now

while process cond process_block s(:block, *body) end endend



Voilà# Running tests:

.......





What Have We Done?


Ryan Davis, Seattle.rbLet’s Write an Interpreter!require "ruby_parser"require "sexp_processor"

class UbyInterpreter < SexpInterpreter VERSION = "1.0.0"

attr_accessor :parser attr_accessor :env

def initialize super

self.parser = Ruby19Parser. new self.env = Environment.new end


def parse src self.parser.process src end

def process_block s result = nil s.rest.each do |sub| result = process sub end result end



if recv then recv.send(msg, *args) else d, body = self.env[msg]

self.env.scope do d.rest.zip(args). each do |k, v| self.env[k] = v end

process_block s(:block, *body) end end end

def process_defn s _, name, args, *body = s

self.env[name] = [args, body]

nil end

def process_false s false end

def process_if s _, c, t, f = s

c = process c

if c then process t else process f end end

def process_lasgn s _, name, val = s

self.env[name] = process val end

def process_lit s s.last end

def process_lvar s _, name = s

self.env[name] end

def process_nil s nil end

def process_true s true end

def process_while s _, cond, *body = s body.pop

while process cond process_block s(:block, *body) end end

class Environment def [] k self.all[k] end

def []= k, v @env.last[k] = v end

def all @env.inject(&:merge) end

def scope @env.push({})

yield ensure @env.pop end

def initialize @env = [{}] end endend



class TestUbyInterpreter < MiniTest::Unit::TestCase attr_accessor :int


def assert_eval exp, src, msg = nil assert_equal exp, int.eval(src), msg end

def define_fib assert_eval nil, <<-END def fib n if n <= 2 then 1 else fib(n-2) + fib(n-1) end end END end

def test_sanity assert_eval 3, "3" assert_eval 7, "3 + 4" end

def test_defn assert_eval nil, <<-EOM n = 24 def double n 2 * n end EOM

assert_eval 42, "double(21)" end

def test_fib define_fib

assert_eval 8, "fib(6)" end

def test_if assert_eval 42, "if true then 42 else 24 end" end

def test_if_falsey assert_eval 24, "if nil then 42 else 24 end" assert_eval 24, "if false then 42 else 24 end" end

def test_lvar assert_eval 42, "x = 42; x" end

def test_while_fib define_fib

assert_eval 1+1+2+3+5+8+13+21+34+55, <<-EOM n = 1 sum = 0 while n <= 10 sum += fib(n) n += 1 end sum EOM endend



“Uby” Language

• Basic numeric types, true, false, nil.• Conditional branching and looping.• Primitive & user defined functions.• Local variables & variable scoping.• Test-driven, extensible, patterns-based design.• ~2 hours, ~130 LOC impl, ~70 LOC test.• Fits in one head.



What Else Can We Do?• Add richer types: strings, arrays, hashes, etc.

• Enforce different scoping rules (eg. ruby's opaque def).

• Implement recursive tail-calls.

• Add an object system.

• Change the way functions are called.



Further Study



Fantastic Books



No time for questions?

Please grab me in the hallway.



"ank You…



Bonus:Life T'



Typeface:L$o(



Rubyb g k p q" ) ∂



Scoring Ligatured Wordsligatures = /NN|OO|TT|Qu|fff|tt|www|[HMN]E|[HN]K|(?:ff|[Tcfs])h|(?:ff|[cfs])k|(?:ff|[cfi])t|(?:ff|it|tt|[frt])y|[is]p|tt?i|O[CG]|i[vw]|ff?[bj]/

dict = File.readlines("/usr/share/dict/words").map(&:chomp)words = Hash.new 0

dict.each do |word| start = 0

hits = word.scan(ligatures) words[word] = hits.size unless hits.empty?end

words.sort_by { |w,v| [-v, w] }.each do |word, score| puts "%2d: %s" % [score, word]end



Ar+!e&onicapen!en#a(,'an!produ"#$



"ank You

Trolls of 2013ryan/presentations/2013_MWRC... · 2013-04-08 · MWRC 2013, Salt Lake City, UT...

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Transcript of Trolls of 2013ryan/presentations/2013_MWRC... · 2013-04-08 · MWRC 2013, Salt Lake City, UT...