Trail Commands
==============

The commands for manipulating the Calc Trail buffer are two-key
sequences beginning with the `t' prefix.

The `t d' (`calc-trail-display') command turns display of the trail on
and off.  Normally the trail display is toggled on if it was off, off
if it was on.  With a numeric prefix of zero, this command always
turns the trail off; with a prefix of one, it always turns the trail
on.  The other trail-manipulation commands described here
automatically turn the trail on.  Note that when the trail is off
values are still recorded there; they are simply not displayed.  To
set Emacs to turn the trail off by default, type `t d' and then save
the mode settings with `m m' (`calc-save-modes').

The `t i' (`calc-trail-in') and `t o' (`calc-trail-out') commands
switch the cursor into and out of the Calc Trail window.  In practice
they are rarely used, since the commands shown below are a more
convenient way to move around in the trail, and they work "by remote
control" when the cursor is still in the Calculator window.

There is a "trail pointer" which selects some entry of the trail at
any given time.  The trail pointer looks like a `>' symbol right
before the selected number.  The following commands operate on the
trail pointer in various ways.

The `t y' (`calc-trail-yank') command reads the selected value in the
trail and pushes it onto the Calculator stack.  It allows you to
re-use any previously computed value without retyping.  With a numeric
prefix argument N, it yanks the value N lines above the current trail
pointer.

The `t <' (`calc-trail-scroll-left') and `t >'
(`calc-trail-scroll-right') commands horizontally scroll the trail
window left or right by one half of its width.

The `t n' (`calc-trail-next') and `t p' (`calc-trail-previous)'
commands move the trail pointer down or up one line.  The `t f'
(`calc-trail-forward') and `t b' (`calc-trail-backward') commands move
the trail pointer down or up one screenful at a time.  All of these
commands accept numeric prefix arguments to move several lines or
screenfuls at a time.

The `t [' (`calc-trail-first') and `t ]' (`calc-trail-last') commands
move the trail pointer to the first or last line of the trail.  The `t
h' (`calc-trail-here') command moves the trail pointer to the cursor
position; unlike the other trail commands, `t h' works only when Calc
Trail is the selected window.

The `t s' (`calc-trail-isearch-forward') and `t r'
(`calc-trail-isearch-backward') commands perform an incremental search
forward or backward through the trail.  You can press RET to terminate
the search; the trail pointer moves to the current line.  If you
cancel the search with `C-g', the trail pointer stays where it was
when the search began.

The `t m' (`calc-trail-marker') command allows you to enter a line of
text of your own choosing into the trail.  The text is inserted after
the line containing the trail pointer; this usually means it is added
to the end of the trail.  Trail markers are useful mainly as the
targets for later incremental searches in the trail.

The `t k' (`calc-trail-kill') command removes the selected line from
the trail.  The line is saved in the Emacs kill ring suitable for
yanking into another buffer, but it is not easy to yank the text back
into the trail buffer.  With a numeric prefix argument, this command
kills the N lines below or above the selected one.

The `t .' (`calc-full-trail-vectors') command is described elsewhere;
See Vector and Matrix Formats.