Land of Lisp binary search algorithm in ruby. This is in stark contrast to my verbose approach in the summer of 2011: http://rand9.com/blog/picking-the-right-number-as-quickly-as-possible/

binary_search.rb

# set some vars
@high = 100
@low = 0

# Simply calc the midpoint (no remainder)
# of the high and low value (bit shift right)
def ask
  (@high + @low) >> 1
end

# Set the lower bound to the midpoint plus 1
# and ask again
def higher
  @low = ask + 1
  ask
end

# Set the upper bound to the midpoint minus 1
# and ask again
def lower
  @high = ask - 1
  ask
end

# Reset the bounds
def reset
  @high = 100
  @low = 0
  ask
end

# Pick your number, then call ask.
# From there simply say wether the number is higher or lower.
# Use reset to... reset the bounds.

ask