Backwards compatibility for Cartesian macros (ngenerate & nsplat)

src/Compat.jl

@@ -2,6 +2,10 @@ module Compat
 
 using Base.Meta
 
+include("ngenerate.jl")
+using .CompatCartesian
+export @ngenerate, @nsplat
+
 if VERSION < v"0.4.0-dev+1419"
     export UInt, UInt8, UInt16, UInt32, UInt64, UInt128
     const UInt = Uint

src/ngenerate.jl

@@ -0,0 +1,141 @@
+module CompatCartesian
+
+export @ngenerate, @nsplat
+
+macro ngenerate(itersym, returntypeexpr, funcexpr)
+    if isa(funcexpr, Expr) && funcexpr.head == :macrocall && funcexpr.args[1] == symbol("@inline")
+        funcexpr = Base._inline(funcexpr.args[2])
+    end
+    isfuncexpr(funcexpr) || error("Requires a function expression")
+    esc(_ngenerate(itersym, funcexpr))
+end
+
+function _ngenerate(itersym::Symbol, funcexpr::Expr)
+    prototype = funcexpr.args[1]
+    body = funcexpr.args[2]
+    varname, T = get_splatinfo(prototype, itersym)
+    ex = Expr(:$, itersym)
+    sreplace!(body, itersym, ex)
+    if !isempty(varname)
+        prototype, body = _nsplat(prototype, body, varname, T, itersym)
+    else
+        body = Expr(:quote, body)
+    end
+    Expr(:stagedfunction, prototype, body)
+end
+
+macro nsplat(itersym, args...)
+    if length(args) == 1
+        funcexpr = args[1]
+    elseif length(args) == 2
+        funcexpr = args[2]
+    else
+        error("Wrong number of arguments")
+    end
+    if isa(funcexpr, Expr) && funcexpr.head == :macrocall && funcexpr.args[1] == symbol("@inline")
+        funcexpr = Base._inline(funcexpr.args[2])
+    end
+    isfuncexpr(funcexpr) || error("Second argument must be a function expression")
+    prototype = funcexpr.args[1]
+    body = funcexpr.args[2]
+    varname, T = get_splatinfo(prototype, itersym)
+    isempty(varname) && error("Last argument must be a splat")
+    prototype, body = _nsplat(prototype, body, varname, T, itersym)
+    esc(Expr(:stagedfunction, prototype, body))
+end
+
+function _nsplat(prototype, body, varname, T, itersym)
+    varsym = symbol(varname)
+    prototype.args[end] = Expr(:..., Expr(:(::), varsym, T)) # :($varsym::$T...)
+    varquot = Expr(:quote, varsym)
+    bodyquot = Expr(:quote, body)
+    newbody = quote
+        $itersym = length($varsym)
+        Compat.CompatCartesian.resolvesplats!($bodyquot, $varquot, $itersym)
+    end
+    prototype, newbody
+end
+
+# If using the syntax that will need "desplatting",
+#     myfunction(A::AbstractArray, I::NTuple{N, Int}...)
+# return the variable name (as a string) and type
+function get_splatinfo(ex::Expr, itersym::Symbol)
+    if ex.head == :call
+        a = ex.args[end]
+        if  isa(a, Expr) && a.head == :... && length(a.args) == 1
+            b = a.args[1]
+            if isa(b, Expr) && b.head == :(::)
+                varname = string(b.args[1])
+                c = b.args[2]
+                if isa(c, Expr) && c.head == :curly && c.args[1] == :NTuple && c.args[2] == itersym
+                    T = c.args[3]
+                    return varname, T
+                end
+            end
+        end
+    end
+    "", Void
+end
+
+resolvesplats!(arg, varname, N) = arg
+function resolvesplats!(ex::Expr, varname, N::Int)
+    if ex.head == :call
+        for i = 2:length(ex.args)-1
+            resolvesplats!(ex.args[i], varname, N)
+        end
+        a = ex.args[end]
+        if isa(a, Expr) && a.head == :... && a.args[1] == symbol(varname)
+            ex.args[end] = :($varname[1]) # Expr(:ref, varname, 1)
+            for i = 2:N
+                push!(ex.args, :($varname[$i])) # Expr(:ref, varname, i))
+            end
+        else
+            resolvesplats!(a, varname, N)
+        end
+    else
+        for i = 1:length(ex.args)
+            resolvesplats!(ex.args[i], varname, N)
+        end
+    end
+    ex
+end
+
+isfuncexpr(ex::Expr) =
+    ex.head == :function || (ex.head == :(=) && typeof(ex.args[1]) == Expr && ex.args[1].head == :call)
+isfuncexpr(arg) = false
+
+sreplace!(arg, sym, val) = arg
+function sreplace!(ex::Expr, sym, val)
+    for i = 1:length(ex.args)
+        ex.args[i] = sreplace!(ex.args[i], sym, val)
+    end
+    ex
+end
+sreplace!(s::Symbol, sym, val) = s == sym ? val : s
+
+# If using the syntax that will need "desplatting",
+#     myfunction(A::AbstractArray, I::NTuple{N, Int}...)
+# return the variable name (as a string) and type
+function get_splatinfo(ex::Expr, itersym::Symbol)
+    if ex.head == :call
+        a = ex.args[end]
+        if  isa(a, Expr) && a.head == :... && length(a.args) == 1
+            b = a.args[1]
+            if isa(b, Expr) && b.head == :(::)
+                varname = string(b.args[1])
+                c = b.args[2]
+                if isa(c, Expr) && c.head == :curly && c.args[1] == :NTuple && c.args[2] == itersym
+                    T = c.args[3]
+                    return varname, T
+                end
+            end
+        end
+    end
+    "", Void
+end
+
+isfuncexpr(ex::Expr) =
+    ex.head == :function || (ex.head == :(=) && typeof(ex.args[1]) == Expr && ex.args[1].head == :call)
+isfuncexpr(arg) = false
+
+end