Recaman Sequence Generator

recaman.rb

#!/usr/bin/ruby

# Recaman Sequence Generator

HIEGHT=2160
WIDTH=3840

SVG_PREAMBLE = <<~HEREDOC
        <?xml version="1.0" standalone="no"?>
        <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
          "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
        <svg width="#{WIDTH}px" height="#{HIEGHT}px" viewBox="-1 #{-1 * HIEGHT / 2} #{WIDTH} #{HIEGHT }"
                  xmlns="http://www.w3.org/2000/svg" version="1.1">
        HEREDOC

SVG_FOOTER = <<~HEREDOC
        </svg>
        HEREDOC

MAX_SEQUENCE_VALUE = 1000000

$current_number = 0
$current_step = 1

$visted_numbers = []
$visted_numbers[0] = true

def iterate_sequence
   if can_go_back?
      $current_number -= $current_step
      $visted_numbers[$current_number] = true
   else
      $current_number += $current_step
      $visted_numbers[$current_number] = true
   end
   $current_step += 1
end

def can_go_back?
   return false if $current_number - $current_step <= 0
   return false if $visted_numbers[$current_number - $current_step]
   return true
end

puts SVG_PREAMBLE

$last_delta_negative = false
$flag = 0
def flip_flag
        if $flag == 0
                $flag = 1
        else
                $flag = 0
        end
end

while $current_number < MAX_SEQUENCE_VALUE
        last_value = $current_number
   iterate_sequence
        delta = $current_number - last_value
        if delta > 0
                unless $last_delta_negative
                        flip_flag
                end
                $last_delta_negative = false
        else
                if $last_delta_negative
                        flip_flag
                end
                $last_delta_negative = true
        end

        puts <<~HEREDOC
        <path d="M#{last_value},0 a0.5,0.5 90 0,#{$flag} #{delta},0" fill="none" stroke="black" stroke-width="0.5" />"
        HEREDOC
end

puts SVG_FOOTER