This spaces over to a given column.
~colnum,colincT will output
sufficient spaces to move the cursor to column colnum. If the cursor
is already at or beyond column colnum, it will output spaces to move it to
column colnum+k*colinc for the smallest positive integer
k possible, unless colinc is zero, in which case no spaces
are output if the cursor is already at or beyond column colnum.
colnum and colinc default to 1.
If for some reason the current absolute column position cannot be determined
by direct inquiry,
format
may be able to deduce the current column position by noting
that certain directives (such as ~%, or ~&,
or ~A
with the argument being a string containing a newline) cause
the column position to be reset to zero, and counting the number of characters
emitted since that point. If that fails, format
may attempt a
similar deduction on the riskier assumption that the destination was
at column zero when format
was invoked. If even this heuristic fails
or is implementationally inconvenient, at worst
the ~T operation will simply output two spaces.
~@T performs relative tabulation.
~colrel,colinc@T outputs colrel spaces
and then outputs the smallest non-negative
number of additional spaces necessary to move the cursor
to a column that is a multiple
of colinc. For example, the directive
~3,8@T outputs
three spaces and then moves the cursor to a "standard multiple-of-eight
tab stop" if not at one already.
If the current output column cannot be determined, however,
then colinc is ignored, and exactly colrel spaces are output.
If the colon modifier is used with the ~T directive,
the tabbing computation is done relative to the horizontal position where the
section immediately containing the directive begins, rather than with
respect to a horizontal position of zero. The numerical parameters are
both interpreted as being in units of ems and both default to 1.
~n,m:T is the same as
(pprint-tab :section n m).
~n,m:@T is the same as
(pprint-tab :section-relative n m).