To duplicate the top object on the stack, press RET or SPC
(two equivalent keys for the calc-enter command).
Given a positive numeric prefix argument, these commands duplicate
several elements at the top of the stack.
Given a negative argument,
these commands duplicate the specified element of the stack.
Given an argument of zero, they duplicate the entire stack.
For example, with `10 20 30' on the stack,
RET creates `10 20 30 30',
C-u 2 RET creates `10 20 30 20 30',
C-u - 2 RET creates `10 20 30 20', and
C-u 0 RET creates `10 20 30 10 20 30'.
The LFD (calc-over) command (on a key marked Line-Feed if you
have it, else on C-j) is like calc-enter
except that the sign of the numeric prefix argument is interpreted
oppositely. Also, with no prefix argument the default argument is 2.
Thus with `10 20 30' on the stack, LFD and C-u 2 LFD
are both equivalent to C-u - 2 RET, producing
`10 20 30 20'.
To remove the top element from the stack, press DEL (calc-pop).
The C-d key is a synonym for DEL.
(If the top element is an incomplete object with at least one element, the
last element is removed from it.) Given a positive numeric prefix argument,
several elements are removed. Given a negative argument, the specified
element of the stack is deleted. Given an argument of zero, the entire
stack is emptied.
For example, with `10 20 30' on the stack,
DEL leaves `10 20',
C-u 2 DEL leaves `10',
C-u - 2 DEL leaves `10 30', and
C-u 0 DEL leaves an empty stack.
The M-DEL (calc-pop-above) command is to DEL what
LFD is to RET: It interprets the sign of the numeric
prefix argument in the opposite way, and the default argument is 2.
Thus M-DEL by itself removes the second-from-top stack element,
leaving the first, third, fourth, and so on; M-3 M-DEL deletes
the third stack element.
To exchange the top two elements of the stack, press TAB
(calc-roll-down). Given a positive numeric prefix argument, the
specified number of elements at the top of the stack are rotated downward.
Given a negative argument, the entire stack is rotated downward the specified
number of times. Given an argument of zero, the entire stack is reversed
top-for-bottom.
For example, with `10 20 30 40 50' on the stack,
TAB creates `10 20 30 50 40',
C-u 3 TAB creates `10 20 50 30 40',
C-u - 2 TAB creates `40 50 10 20 30', and
C-u 0 TAB creates `50 40 30 20 10'.
The command M-TAB (calc-roll-up) is analogous to TAB
except that it rotates upward instead of downward. Also, the default
with no prefix argument is to rotate the top 3 elements.
For example, with `10 20 30 40 50' on the stack,
M-TAB creates `10 20 40 50 30',
C-u 4 M-TAB creates `10 30 40 50 20',
C-u - 2 M-TAB creates `30 40 50 10 20', and
C-u 0 M-TAB creates `50 40 30 20 10'.
A good way to view the operation of TAB and M-TAB is in terms of moving a particular element to a new position in the stack. With a positive argument n, TAB moves the top stack element down to level n, making room for it by pulling all the intervening stack elements toward the top. M-TAB moves the element at level n up to the top. (Compare with LFD, which copies instead of moving the element in level n.)
With a negative argument -n, TAB rotates the stack to move the object in level n to the deepest place in the stack, and the object in level n+1 to the top. M-TAB rotates the deepest stack element to be in level n, also putting the top stack element in level n+1.
See section Selecting Sub-Formulas, for a way to apply these commands to any portion of a vector or formula on the stack.