- time -

This file defines the type
'time' over which most tables run.

It also displays the values of the
time points.
In the original spreadsheet, 
column A displayed these.
They aren't used in the
calculations, but I've left them
in for completeness.


-- time --

  type time = 1:500.


-- time_point --

time_point[ t ] displays the time
at t. This is just t. 

  table time_point : time -> general.

  time_point[ 1 ] = 
    1.

  time_point[ t > 1 ] = 
    time_point[ t-1 ] + 1.