I haven't had time to do any "extra credit" stuff, or
even test this fully, but here goes -
For what it's worth, here's the test code I've written to test submissions. I'm not 100% sure that it's correctly testing things yet, but I think it is 
The interesting bit for me has been trying to identify any solution that ignores requirement #2, such as solutions that always show the correct time, or that are always a bit fast or slow. The statistics are my best attempt at that so far.
To use, if you have defined your class name as "FuzzyTime", just include this file after your class definition. (Beware long incorrectly wrapped lines ahead.)
require 'test/unit'
$DEBUG = false
class Time
def short
strftime("%H:%M")
end
def to_fuzzy
s = short
s[4] = "~"
s
end
end
class FuzzyTimeTester < Test::Unit::TestCase
def test_running
runs, num_ahead, num_behind = 0, 0, 0
20.times{
t = Time.at( Time.new + rand( 3600 * 300 ) )
advance_seconds = rand( 200 ) + 17
end_time = t + 60 * 60 * 24
ft = FuzzyTime.new( t )
last_value = nil
while( t < end_time )
assert_equal t, ft.actual
t0 = Time.at( t - 60 * 5 )
t2 = Time.at( t + 60 * 5 )
legal_values = [ t0, t, t2 ].map{ |x| x.to_fuzzy }.uniq
if last_value
y,mon,day = t.year, t.mon, t.day
h,m = last_value.scan(/\d+/).map{ |s| s.to_i }
m *= 10
if (m -= 10) < 0
m %= 60
if (h -= 1) < 0
h %= 24
end
end
illegal_old_value = Time.local( y,mon,day,h,m ).to_fuzzy
legal_values -= [ illegal_old_value ]
if $DEBUG
puts "Now: #{t.short}; legal: #{legal_values.inspect} (was #{last_value}, can't be #{illegal_old_value})"
end
end
s = ft.to_s
assert legal_values.include?( s ), "#{s} not in #{legal_values.inspect}"
a = t.to_fuzzy
if s != a
ahour, amin = a.scan( /\d+/ ).map{ |x| x.to_i }
fhour, fmin = s.scan( /\d+/ ).map{ |x| x.to_i }
if fmin > amin || fhour > ahour || ( fhour == 0 && ahour == 23 )
num_ahead += 1
else
num_behind +=1
end
end
runs += 1
last_value = s
ft.advance( advance_seconds )
t += advance_seconds
end
puts "Variation: %.2f%% ahead, %.2f%% behind" % [ 100.0 * num_ahead / runs, 100.0 * num_behind / runs ]
}
end
end
路路路
From: Robert Conn [mailto:bob.conn@btinternet.com]
