Stair-climbing puzzle: Difference between revisions

=={{header|Ruby}}==

<lang ruby>def step_up

start_position = $position

step until ($position == start_position + 1)

end

# assumptions about the step function:

# - it maintains the current position of the robot "as a side effect"

# - the robot is equally likely to step back as to step up

def step

if rand < 0.5

$position -= 1

p "fall (#$position)" if $DEBUG

return false

else

$position += 1

p "rise (#$position)" if $DEBUG

return true

end

end

$position = 0

step_up</lang>

Sample run:

<pre>$ ruby -d stair.climbing.rb

"fall (-1)"

"rise (0)"

"fall (-1)"

"rise (0)"

"fall (-1)"

"fall (-2)"

"rise (-1)"

"rise (0)"

"rise (1)"</pre>