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.

Beiträge, die die Anforderungen erfüllen

#!/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)))))

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);
}

Nu aber wirklich noch in Perl:

#!/usr/bin/perl

@flo = ( "dividuum", "syb", "fiji", "flowhase" );

for $i (0..$#flo) {
  eval "\$flo$i = \$flo\[$i\]";
  print "\$flo$i eq \"" . eval("\$flo$i") . "\"\n";
}

Gute alte Bash:

#!/bin/sh

flo="dividuum syb fiji flowhase"

n=0
for f in $flo
do
  eval flo$n=$f
  echo -n "flo$n == "
  eval echo \$flo$n
  n=$(($n+1))
done

Realisiert in PHP, Lisp, Perl, XML, Bash und XSLT und immernoch kürzer als die C-Version:

<?php $flo = array( "dividuum", "syb", "fiji", "flowhase" ); $l = fopen("flo.lisp", "w"); $p = fopen("flo.pl", "w"); fwrite($l, '(progn (format t "~a" "<flo>")'); fwrite($p,' print <<EOF <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns="http://www.w3.org/TR/xhtml1/strict"> <xsl:template match="/">'); for($i=0;$i<count($flo);$i++) { fwrite($l, "(format t \"~a~a~a\" \"<flo$i>\" \"$flo[$i]\" \"</flo$i>\")"); fwrite($p, "flo$i == <xsl:value-of select=\"flo/flo$i\"/>\n"); } fwrite($l, '(format t "~a" "</flo>"))'); fwrite($p,' </xsl:template> </xsl:stylesheet> EOF'."\n"); fclose($l); fclose($p); system("sbcl --noinform --load flo.lisp --eval '(quit)' > flo.xml"); system("perl flo.pl > flo.xslt"); system("xsltproc flo.xslt flo.xml"); ?>

http://static.php.net/www.php.net/images/news/php-logo.gif http://www.mail-archive.com/copenhagen@perl.org/msg00162/logo_mermaid.png

Bloatiger Angebercode, der auch noch etwas völlig anderes macht

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: (Zumindest) 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)))

Fußnoten

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()])