Flo

Wir weisen darauf hin, dass möglicherweise nicht alle Beiträge den Anforderungen genügen. Die Anforderungen sind: Flos sind in Liste "flo" gespeichert, zur Ausführ- oder Compilierzeit werden durch den Code einzelne flo0, flo1, flo2, flo3 Variablen angelegt, die später dann auch zur Ausgabe verwendet werden.

#!/usr/bin/env ruby

flo = [ "dividuum", "syb", "fiji", "flowhase" ]

# flos sind keine arrayss1!
for i in 0..flo.size-1
  eval "flo#{i} = flo[#{i}]"
  puts "flo#{i} == \"" + eval("flo#{i}") + "\""
end

Dieses Perl (*duck*) kann ja keiner lesen!¹⁾ Daher:

(eval-when (:compile-toplevel :load-toplevel :execute) (defvar *flo-sequence* #("dividuum" "syb" "fiji" "flowhase"))) (defmacro make-individual-flo-variables () (cons 'progn (loop for flo across *flo-sequence* for i from 0 collect `(defvar ,(read-from-string (format nil "*flo~d*" i)) ,flo)))) (make-individual-flo-variables) (dotimes (i 4) (format t "~&flo~d = ~a" i (eval (read-from-string (format nil "*flo~d*" i)))))

Und nun nochmal Ruby mit viel bloatigem Metaprogramming-Foo (Und etwas völlig anderes machend. Anm. v. mgr):

#!/usr/bin/env ruby
class Flo
  def self.metaclass; class << self; self; end; end
  def self.traits(*arr)
    return @traits if arr.empty?
    attr_accessor *arr
    arr.each do |a|
      metaclass.instance_eval do
        define_method( a ) do |val|
          @traits ||= {}
          @traits[a] = val
        end
      end
    end
    class_eval do
      define_method( :initialize ) do
        self.class.traits.each do |k,v|
          instance_variable_set("@#{k}", v)
        end
      end
    end
  end

  traits :name, :skill, :notebook

  def to_s
    s = "#{self.class} is actually #{self.name} and is good at #{self.skill}\n\tHe loves hacking on his #{self.notebook}"
  end
end

class Flo0 < Flo
  name "dividuum"
  skill "DOOM"
  notebook "old Dell"
end

class Flo1 < Flo
  name "Peter"
  skill "math"
  notebook "IBM Thinkpad"
end
class Flo2 < Flo
  name "Fiji"
  skill "WOW"
  notebook "i have no idea"
end

class Flo3 < Flo
  name "flowhase"
  skill "hoppeln"
  notebook "hasIbook"
end

a = [ Flo0.new, Flo1.new, Flo2.new, Flo3.new ]
a.each { |f| puts f }

Und nochmal das, was das Ruby-Programm "mit viel bloatigem Metaprogramming-Foo" macht, allerdings wiederum in Common Lisp gegossen:
(Warnung: Als Lispprogramm ist dieses Beispiel ziemlich unsinning, und z.B. die PRINT-OBJECT-Methode widerspricht der gängigen Konvention.)

(defclass flo ()
  ((name :initarg :name :reader flo-name)
   (skill :initarg :skill :reader flo-skill)
   (notebook :initarg :notebook :reader flo-notebook)))

(defun slot-value-or-something (object &key (slot 'name) (something "without name"))
  (if (slot-boundp object slot)
      (slot-value object slot)
      something))

(defmethod print-object ((flo flo) stream)
  (format stream "~&~a is actually ~a and is good at ~a.~&He loves hacking on his ~a."
          (class-name (class-of flo))
          (slot-value-or-something flo)
          (slot-value-or-something flo :slot 'skill    :something "nothing")
          (slot-value-or-something flo :slot 'notebook :something "dulcimer")))

(defmacro def-flo-class (class-name &key name skill notebook)
  (macrolet ((make-slot-def (name)
               `(when ,name
                  `(,',name :initform ,,name))))
  `(defclass ,class-name (flo)
     ,(remove nil (list
                   (make-slot-def name)
                   (make-slot-def skill)
                   (make-slot-def notebook))))))

(def-flo-class |Flo0|
    :name "dividuum"
    :skill "DOOM"
    :notebook "old Dell")

(def-flo-class |Flo1|
    :name "Peter"
    :skill "math"
    :notebook "IBM Thinkpad")

(def-flo-class |Flo2|
    :name "Fiji"
    :skill "WOW"
    :notebook "I-have-no-idea")

(def-flo-class |Flo3|
    :name "flohase"
    :skill "hoppeln"
    :notebook "hasIbook")

(let ((flos (list (make-instance '|Flo0|)
                  (make-instance '|Flo1|)
                  (make-instance '|Flo2|)
                  (make-instance '|Flo3|))))
  (dolist (flo flos)
    (print flo)))

dreckig:

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>

const int flolen = 4;
static char *flos[] = {"dividuum","syb","fiji","flowhase"};
static char *proghead = "#include <stdio.h>\n"
                        "int main(void){\n";
static char *progend =  "  return(0);\n"
                        "}\n";

int main(void){
        int i;
        FILE *o;
        o=fopen("flo2.c","w");
        fputs(proghead,o);
        for(i=0;i<flolen;i++){
                fprintf(o,"  char *flo%d = \"%s\";\n",i,flos[i]);
                fprintf(o,"  printf(\"flo%%d ist %%s\\n\",%d,flo%d);\n",i,i);
        }
        fputs(progend,o);
        fclose(o);
        system("/usr/bin/gcc -o flos flo2.c;./flos;rm -f flo2.c flos");
        return(0);
}

---

1) Anmerkung zu: "Dieses Perl (*duck*) kann ja keiner lesen!"

Stimmt doch gar nicht! Ist ganz einfach:

map printf("%s = %s\n", [flo0..flo3]->[$_], [dividuum, syb, fiji, flowhase]->[$_]), 0..$#{@{[flo0..flo3]}};

(Kommentar von mgr: Genau, "0..$#{@{[flo0..flo3]}}" ... q.e.d. Danke für das gute Beispiel. Aber ernsthaft, es ging hier eben gerade *nicht* um Einzeiler, die will niemand.)

Und auch in python kann man Einzeiler schreiben:

print "\n".join(["%s = %s" % (k, v) for k, v in {"flo0":"dividuum", "flo1":"syb", "flo2":"fiji", "flo3":"flowhase"}.items()])