Julia Taiwan 5th meetup

1. Metaprogramming in Julia
Julia Taiwan發起人 杜岳華

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pre-processor
compiler
assembler
linker
memory
loader

14. Runtime
Compile time
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pre-processor
compiler
assembler
linker
memory
loader

15. Compile time
pre-processor
compiler
assembler
linker
Macro processing, augmentation,
file inclusion, language extension
Generate target assembly code
Generate relocatable machine code
(object file)
Links object files and generate
executable machine code (binary file)

16. Runtime
memory
loader
Loader (part of OS) loads
programs and libraries
Execution

17. Compile time
pre-processer
compiler
assembler
linker
Lexical analysis
Syntax analysis
Semantic analysis
Intermediate code
generation
Optimization
Code generation

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19. Compiler
Lexical analysis
Syntax analysis
Semantic analysis
scannerIdentify tokens
parser
Identify the grammar and
establish the parsing tree
checkerType checking, declaration

20. Compiler
Intermediate code
generation
Optimization
Code generation
Generate machine independent code for
common optimization
Optimization! Some magics……
Generate assembly code
Interpreter

21. Source code
Tokens
AST
Lowered AST
Typed AST
LLVM IR
LLVM IR
Instructions
lexing
parsing
lowering
type inference
LLVM codegen
optimize
native codegen
LLVM IRLLVM IRMacro
expansion
Generated
function
JIT

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julia> :foo
:foo
julia> :bar
:bar

24. julia> :foo == Symbol("foo")
true
julia> Symbol("func",10)
:func10
julia>
Symbol(:var,'_',"sym")
:var_sym

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26. julia> ex1 = parse(“1 + 1”)
:(1 + 1)
julia> typeof(ex1)
Expr

27. julia> ex1.head
:call
julia> ex1.args
3-element Array{Any,1}:
:+
1
1
julia> ex1.typ
Any

29. julia> dump(ex1)
Expr
head: Symbol call
args: Array{Any}((3,))
1: Symbol +
2: Int64 1
3: Int64 1
typ: Any

31. julia> dump(ex)
Expr
head: Symbol call
args: Array{Any}((4,))
1: Symbol +
2: Symbol a
3: Expr
head: Symbol call
args: Array{Any}((3,))
1: Symbol *
2: Symbol b
3: Symbol c
typ: Any
4: Int64 1
typ: Any
julia> ex = :(a + b * c + 1)
:(a + b * c + 1)

32. julia> dump(ex)
Expr
head: Symbol call
args: Array{Any}((4,))
1: Symbol +
2: Symbol a
3: Expr
head: Symbol call
args: Array{Any}((3,))
1: Symbol *
2: Symbol b
3: Symbol c
typ: Any
4: Int64 1
typ: Any

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julia> eval(:(1 + 2))
3

34. julia> a = 1
1
julia> ex = :a
:a
julia> eval(ex)
1

35. julia> a = 1;
julia> ex = :($a + b)
:(1 + b)

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julia> macro sayhello()
return :( println("Hello, world!") )
end
@sayhello
julia> @sayhello
Hello, world!

37. julia> macro sayhello(name)
return :( println("Hello, ", $name) )
end
@sayhello
julia> @sayhello("Bob")
Hello, Bob
julia> @sayhello "Bob"
Hello, Bob

38. parse → expressions → macro → new expr. → compile

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for op = (:+, :*, :&, :|, :$)
eval(quote
($op)(a,b,c) = ($op)(($op)(a,b),c)
end)
end

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julia> macro decorator(dec, func)
name = func.args[1].args[1]
hiddenname = gensym()
func.args[1].args[1] = hiddenname
quote
$func
const $(esc(name)) = $dec($hiddenname)
end
end
http://julia-programming-language.2336112.n4.nabble.com/Macro-as-decorators-td40521.html

41. julia> foo(f) = x -> 2*f(x+10);
julia> @decorator foo function bar(x)
return x+1
end
julia> bar(0)
22

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43. julia> @generated function foo(x)
println(x)
return :(x*x)
end
foo (generic function with 1 method)

44. julia> x = foo(2);
Int64
julia> x
4

45. julia> y = foo("bar");
String
julia> y
"barbar"

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julia> @generated function bar(x)
if x <: Integer
return :(x^2)
else
return :(x)
end
end
bar (generic function with 1 method)
julia> bar(4)
16
julia> bar("baz")
"baz"

48. Source code
Tokens
AST
Lowered AST
Typed AST
LLVM IR
LLVM IR
Instructions
lexing
parsing
lowering
type inference
LLVM codegen
optimize
native codegen
LLVM IRLLVM IR
Expr
Symbol
@code_lowered
@code_typed
@code_llvm
@code_native
@code_warntype

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