clock_equations

Figure out the simple equations that can be made from the time on a digital clock

My 9-year old daughter Chloe and I like to look at the digital clock sometimes and make equations out of the numbers. For example, 12:02 could be 1*2+0 = 2, and 12:03 could be 1+2 = 0+3.

I thought it would be fun to code up a program to find all the "clock eauations". There are two parts: generating the equations, and evaluating their truth value. Generating the equations done one of two ways:

• clock.rb uses a sequence of .lazy enumerators to generate the times, build all possible equations from the numbers of each tine, and filter the valid equations.

• enum_clock.rb uses explicit enumerators of various kinds, mostly to see how things weould come out if I coded them up;

  Enumerator

  Standard Ruby Enumerator

  FiberEnumerator

  Enumerator using Fiber (fiber_enumerator.rb). This is straightforward.
  

  CallccEnumerator

  Enumerator using bare callcc (callcc_enumerator.rb). This one is not particularly nice or well-done.

  CoroutineEnumerator

  Enumerator that encapsulates the callcc usage into a Coroutine class. This one is pretty good. (coroutine_enumerator.rb, coroutine.rb)

  The `Enumerator` class can be set by editing enum_clock.rb and setting variable `UseEnumerator` to the proper class (ugh).

The equations' truth values are determined using a recursive descent expression evaluator.