Canon Cat Reference Manual page 84

A
given variable
name can be
defined
in only
one place.
Thus
you cannot
have
price:5.00
in
one place
and
price
:7
.50
inanother.
If
you try
to
define the
same
variable
in more than one place, you get
a
beep
and
[EXPLAIN]
tells
you
that
variables
can
only
be
defined
once. This
means
that
if
you want
to change the
value of
a
variable, you must
leap to the
place
where
you defined
it originally, unpocket
the
definition of
the
variable,
and
redefine it by
editing
the
text on the
right
side
of
the
colon.
If
you can't
remember
where you
defined
a
variable, unpocket
all
calculations
by
highlighting the
entire
text
and
using
[cnlc].
When
[CALC]
finishes, leap to
your
variable name
followed by
a
colon
(see
Multiple Unpocketing, page 83).
If
you try
to
use a
variable in
an
expression before
defining
the
variable. the Cat
won't
be able to
calculate
it.
The
result
displayed
on your
screen
will
be
????.??.
If
you
use
[OALC]
to define
the
variable at
a
later time, the ??22.2?
will
change
to the correct calculated value.
Column Operators
A
column
of
numbers is a
set
of numbers lined
up
verti-
cally.
Columns look this way on
your
screen,
but the Cat
cannot
literally
see
the
screen,
so
it
finds
columns by
counting tab characters
in
the lines
of
text.
A
/ine is the
text
between
two
break characters
(a
break character
is
a
return, page,
or
document character).
The
first column
in
a
line is the text
following
the
break that
begins the
line
up
to the
first
tab
or
break
character. The
second
column is
the
text
following
the
first
tab up
to
the
next tab
or break. The
third
column is the text
following
the
second
tab,
up to the
next
tab
or break, and
so
on.
If
there is no
text after the break character or between tabs,
the
column is
empry.
The point
is
that
while you
are used
to
thinking of columns
as
vertically
aligned text, they
don't
have to be
vertically
aligned
for
the Cat to use
them. They
just
have to
have the
same
number
of
tab
characters between them.
Even more important, numbers that
are
vertically aligned
may
not be
in the
same
column.
One
of
the
numbers
might
have
two
tab characters
to its
left. while
the
other
has one.
If
so,
the
Cat won't
"see"
them
as
belonging to the
same
column. You
must be
careful
to keep
your
tab
characters
uniform when working
with
columns.
Returns
must
also be
uniform.
For the Cat to work on
the
numbers
in
a column, the lines containing the
numbers
must be separated
by no more than
one refurn. You
can
easily add the numbers
in
a
table,
but not
if
there is
a
blank
line
between any
of
the
lines of text.