Lua Anatomic Programming Functions

 11 July 16:37   In Lua, as in Lisp, functions are a affectionate of data type; you can accredit them to variables and canyon them about in your code.

    Functions can be authentic in the accustomed way, and we can alarm them.

    

> action double(x) acknowledgment x> acknowledgment double(1)

    2

    We can admission the action item created artlessly by using its name after any parentheses. Appropriately we can canyon the action as an argument, abundance it in a data structure, etc.

    

> acknowledgment double

    function: 0x806a5e8

    > a =  -- creates an array

    > acknowledgment bifold  Anatomic Arguments  0 then acknowledgment  end

      if func(arr[1]) then

        acknowledgment lisp_remove_if(func, cdr(arr))

      else

        acknowledgment cons(arr[1], lisp_remove_if(func, cdr(arr)))

      end

    end

    Compare with the afterward Lisp code:

    

(defun our-remove-if (fn lst)

      (if (null lst)

          nil

        (if (funcall fn (car lst))

    (our-remove-if fn (cdr lst))

          (cons (car lst) (our-remove-if fn (cdr lst))))))

    Both the Lua and Lisp cipher aloft are tail-recursive safe (see Appendage Recursion below). (Most implementations for both languages abutment tail-recursion optimising.) Just for comparison, heres how I would cipher a authentic Lua version:

    

function lua_remove_if(func, arr)

      bounded new_array = 

      for _,v in arr do

        if not func(v) then table.insert(new_array, v) end

      end

      acknowledgment new_array

    end

    In Lua, we accept to ascertain the abettor functions cdr and cons which is congenital into Lisp, but using the remove_if is absolutely easy:

    

> t = lisp_remove_if(function(x) acknowledgment math.mod(x,2)==0 end, )

    > acknowledgment table.concat(t,,)

    1,3,5