This procedure was developed to visualize patterns in the
continued fraction expansion of a real number.
It computes 1600 integer partial quotients by default
but this can
be changed to a maximum of 10000 by the 2nd argument.
It reduces these partial quotients modulo 10 by default
(or modulo the 3rd argument). It uses 10 colors by default or
the number specified by the 3rd argument to color the
partial quotients.
In addition, the default grid is approximately square but
this can be changed by means of the fourth argument which is
the number of columns of the first row.