You could also use something called functors which basically are types that
overload the call function. When you pass these as argument the compiler
can specialize the function on the type of the functor and thus inline the
call. See here for example for them being used effectively for performance
increase: https://github.com/JuliaLang/julia/pull/11685
As an example I took the code for insertionsort and made it instead accept
an argument f which will be the functor. I then create some functors to
sort on the different type fields and show an example how sort is called.
function sort!(v::AbstractVector, f, lo::Int=1, hi::Int=length(v))
@inbounds for i = lo+1:hi
j = i
x = v[i]
while j > lo
if f(x, v[j-1])
v[j] = v[j-1]
j -= 1
continue
end
break
end
v[j] = x
end
return v
end
# Some type
immutable CompType
a::Int
b::Int
c::Int
end
b = [CompType(1,2,3), CompType(3,2,1), CompType(2,1,3)]
# Functors
immutable AFunc end
call(::AFunc, x, y) = x.a < y.a
immutable BFunc end
call(::BFunc, x, y) = x.b < y.b
immutable CFunc end
call(::CFunc, x, y) = x.c < y.c
# Can now sort with good performance
sort!(b, AFunc())
println(b)
sort!(b, BFunc())
println(b)
sort!(b, CFunc())
println(b)
Now, this is of course not optimal to rip code out of base. It would be
better if we could pass a functor straight to Base.sort!.
On Wednesday, June 17, 2015 at 8:13:41 PM UTC+2, Ben Ward wrote:
>
> Hi, I want to create a macro with which I can create a function with a
> custom bit of code:
>
> In the repl I can do a toy example:
>
>
> *name = :hi*
>
>
> *vectype = Vector{Int}*
>
>
> *quote** function ($name)(v::$vectype)*
>
> *println("hi")*
>
> *end*
>
> *end*
>
> However if I try to put this in a macro and use it I get an error:
>
> *macro customFun(vectype::DataType, name::Symbol)*
>
>
> * quote** function ($name)(v::$vectype)*
>
> * println("hi World!")*
>
> * end*
>
> * end*
>
>
>
> *end*
>
> *@customFun(Vector{Int}, :hi)*
>
> What am I doing wrong? I'd like to use macro arguments to provide a
> function's name, and the datatype of the argument. I haven't used macros to
> define functions more complex than simple one liners.
>
> Thanks,
> Ben.
>
