hello-world-generator.rb

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-

# Makes a "Hello, world!" program that has no literals.

class HelloWorldGenerator1
  def initialize(s = "Hello, world!")
    @message = s.chomp + "\n"
  end

  def start
    binfile = "hw"
    srcfile = binfile + ".c"
    open(srcfile, "w") do |f_out|
      f_out.puts <<'EOS'
#include <stdio.h>

int c;

main(void)
{
EOS
      c = 0
      @message.each_char do |chr|
        new_c = chr.ord
        if new_c > c
          (new_c - c).times { f_out.puts "  c++;"}
        elsif new_c < c
          (c - new_c).times { f_out.puts "  c--;"}
        end
        f_out.puts "  putchar(c);"
        c = new_c
      end

      f_out.puts <<'EOS'
}
EOS
    end

    command = "cc -o #{binfile} #{srcfile}"
    puts command
    system(command)
    command = "./#{binfile}"
    puts command
    system(command)
  end
end

class HelloWorldGenerator2
  def initialize(s = "Hello, world!")
    @message = s.chomp
  end

  def start
    binfile = "hw"
    srcfile = binfile + ".c"
    open(srcfile, "w") do |f_out|
      f_out.puts <<'EOS'
#include <stdio.h>

int o;
int a, b, c, d, e, f, g, h;

int main(void)
{
  h++;
  g = h + h;
  f = g + g;
  e = f + f;
  d = e + e;
  c = d + d;
  b = c + c;
  a = b + b;

EOS
      vars = "abcdefgh".split(//)
      @message.each_char do |chr|
        expr = ("%08b" % chr.ord).
          split(//).zip(vars).map {|b, v| b == "1" ? v : nil}.
          compact.join(" + ")
        expr = "o" if expr.empty?
        f_out.puts "  putchar(#{expr});"
      end

      f_out.puts <<'EOS'

  puts((char *)&o);

  return o;
}
EOS
    end

    command = "cc -o #{binfile} #{srcfile}"
    puts command
    system(command)
    command = "./#{binfile}"
    puts command
    system(command)
  end
end

class HelloWorldGenerator < HelloWorldGenerator2; end

if __FILE__ == $0
  HelloWorldGenerator.new(ARGV.shift || "Hello, world!").start
end