Btukfyl

If I have a method

macro doarray(arr)

    if in(:head, fieldnames(typeof(arr))) && arr.head == :vect

        println("A Vector")

    else

        throw(ArgumentError("$(arr) should be a vector"))

    end

end

it works if I write this

@doarray([x])

or

@doarray([:x])

but the following code rightly does not work, raising the ArgumentError(i.e. ArgumentError: alist should be a vector).

alist = [:x]

@doarray(alist)

How can I make the above to act similarly as @doarray([x])

Motivation:
I have a recursive macro(say mymacro) which takes a vector, operates on the first value and then calls recursively mymacro with the rest of the vector(say rest_vector). I can create rest_vector, print the value correctly(for debugging) but I don't know how to evaluate rest_vector when I feed it to the mymacro again.

EDIT 1:
I'm trying to implement logic programming in Julia, namely MiniKanren. In the Clojure implementation that I am basing this off, the code is such.

(defmacro fresh

  [var-vec & clauses]

  (if (empty? var-vec)

    `(lconj+ ~@clauses)

    `(call-fresh (fn [~(first var-vec)]

                   (fresh [~@(rest var-vec)]

                     ~@clauses)))))

My failing Julia code based on that is below. I apologize if it does not make sense as I am trying to understand macros by implementing it.

macro fresh(varvec, clauses...)

    if isempty(varvec.args)

        :(lconjplus($(esc(clauses))))

    else

        varvecrest = varvec.args[2:end]

        return quote

            fn = $(esc(varvec.args[1])) -> @fresh($(varvecvest), $(esc(clauses)))

            callfresh(fn)

        end

    end

end

The error I get when I run the code @fresh([x, y], ===(x, 42))(you can disregard ===(x, 42) for this discussion)

ERROR: LoadError: LoadError: UndefVarError: varvecvest not defined

The problem line is fn = $(esc(varvec.args[1])) -> @fresh($(varvecvest), $(esc(clauses)))

If I understand your problem correctly it is better to call a function (not a macro) inside a macro that will operate on AST passed to the macro. Here is a simple example how you could do it:

function recarray(arr)

    println("head: ", popfirst!(arr.args))

    isempty(arr.args) || recarray(arr)

end



macro doarray(arr)

    if in(:head, fieldnames(typeof(arr))) && arr.head == :vect

        println("A Vector")

        recarray(arr)

    else

        throw(ArgumentError("$(arr) should be a vector"))

    end

end

Of course in this example we do not do anything useful. If you specified what exactly you want to achieve then I might suggest something more specific.