_{Release/Master}

Installing

julia 0.6:

Pkg.add("ExpressionPatterns")

Otherwise:

Pkg.clone("https://github.com/fcard/ExpressionPatterns.jl")

# julia 0.5
Pkg.checkout("ExpressionPatterns", "julia-v0.5")

# julia 0.4
Pkg.checkout("ExpressionPatterns", "julia-v0.4")

Matching

using ExpressionPatterns.Matching

m1 = matcher(:(x+y))

m1(:(1+2)) == true
m1(:(1-2)) == false

m2 = matcher(:(f(*{args})))

m2(:(g(1,2))) == true
m2(:(h()))    == true
m2(:(x+y))    == true
m2(:(A{T}))   == false

Destructuring

using ExpressionPatterns.Destructuring

@letds (x+y)=:(1+2) begin
  x,y == (1,2)
end

@macrods first_arg(f(first,*{rest})) first

@first_arg(f(1,2)) == 1

gettype = @anonds (a::T) -> T
gettype(:(x::Integer)) == :Integer

@funds getvalue(a::T) = a
getvalue(:(x::Integer)) == :x

Dispatch

using ExpressionPatterns.Dispatch

@metafunction getpath(M.m) = [getpath(M); m] # this defines the getpath(args...) method
getpath(M::Symbol) = [M]

getpath(:(M1.M2.m)) == [:M1, :M2, :m]

@macromethod inverse_op(x+y) :($x-$y)
@macromethod inverse_op(x-y) :($x+$y)
@macromethod inverse_op(x*y) :($x/$y)
@macromethod inverse_op(x/y) :($x*$y)

@inverse_op(10+20) == -10
@inverse_op(10-20) ==  30
@inverse_op(10*20) ==  .5
@inverse_op(10/20) == 200

# macros created with @macromethod can be extended in other modules

module M1
using ExpressionPatterns.Dispatch
@macromethod f(x+y) 1
end

module M2
using ExpressionPatterns.Dispatch
@metamodule import ..M1.@f
@macromethod f(x-y) 2
end

M1.@f(1+2) == 1
M1.@f(1-2) == 2

Dispatch Reflection

using ExpressionPatterns.Dispatch
using ExpressionPatterns.Dispatch.Reflection

@macromethod f(x+y, z)[method1] = [x,y]
@macromethod f(z, x+y)[method2] = [x,y]

@whichmeta @f(x+y,y+x) #> f(x+y, z)

@prefer @f(z, x+y) over @f(x+y, z)

@whichmeta @f(x+y,y+x) #> f(z, x+y)

@prefer method1 over method2 in @f

@whichmeta @f(x+y,y+x) #> f(x+y, z)

@metaconflicts @f #> <<z> <x+y>> | <<x+y> <z>>

@remove @f(z,x+y)

@metaconflicts @f #> nothing

See Language.md for information on the pattern language.

See the examples or the tests for more uses.

Y'all should also check MacroTools, which inspired me to remake and publish this in the first place!