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Section 2 - Stack Manipulation
When working on the HP49G+ in RPN mode we sometimes make use of the stack manipulation commands that are available
in the STACK menu. These tend to be much more important in programming. With the calculator in RPN mode, the
STACK menu can be found by pressing TOOL F3-STACK or LS PRG F1-STACK. There are 19 stack manipulation
commands in this menu. These are listed and explained in the table below because they don't seem to be explained anywhere
in UG.
| DUP |
Duplicates the item on level 1 of the stack, puts it on level 1 of
the stack and moves everything else up on the stack. |
| SWAP |
Interchanges the items on levels 1 and 2 of the stack |
| DROP |
Deletes the item on level 1 of the stack and drops everything
else down one level. |
| OVER |
Makes a copy of the item from level 2 of the stack, puts it
on level 1, and moves everything else up one level. |
| ROT |
Rotates the item in level 3 of the stack to level 1, the item
from level 1 to level 2, and the item from level 2 to level 3. |
| UNROT |
Reverses the process of ROT. |
| ROLL |
With an integer n in the command line, ROLL works like
ROT, but on the first n levels of the stack, so 3 ROLL has
the same effect as ROT. If the command line in empty but
there is an integer n on level 1 of the stack, ROLL takes n
from the stack, drops the rest of the stack down one level,
then performs the ROLL. Thus, 4 ROLL and 4 ENTER
ROLL have the same effect. |
| ROLLD |
Reverses ROLL |
| PICK |
With an integer n in the command line, PICK works like
OVER, but selects the item from level n of the stack, 2
PICK is the same as OVER. If the command line is empty
and an integer n is on level 1 of the stack, PICK removes the
integer from the stack, moves everything down one level,
then performs the PICK, thus 4 PICK and 4 ENTER PICK
have the same effect. |
| UNPICK |
Is NOT quite the reverse of PICK. With an integer n in the
command line, PICK removes the item in level 1 of the
stack, moves everything in the stack down one level, then
replaces the item in level n with the item that was originally
removed from level 1. If the command line is empty and
there is an integer n on level 1 of the stack, UNPICK
removes the integer from the stack, moves everything in the
stack down one level, then performs the UNPICK, thus 4
UNPICK and 4 ENTER UNPICK have the same effect. |
| PICK3 |
The same as 3 PICK |
| DEPTH |
Counts the number of elements in the stack, puts the number
on level 1 of the stack and moves everything else up one level. |
| DUP2 |
Duplicates the items in levels 1 and 2 of the stack and moves
everything up 2 levels. |
| DUPN |
With an integer n in the command line, DUPN duplicates the
items in levels 1 through n and moves everything up n on the
stack. If the command line is empty and there is an integer n
on level 1 of the stack, DUPN takes the n from the stack,
drops everything down one level, then executes the DUPN.
Thus, 3 DUPN and 3 ENTER DUPN have the same effect. |
| DROP2 |
Drops the items on levels 1 and 2 of the stack and moves
everything else down two levels. |
| DROPN |
With an integer n in the command line, DROPN drops the
items on levels 1 through n from the stack and moves
everything else down n levels. If the command line is empty
and there is an integer n on level 1 of the stack, DROPN
removes the n, drops everything down one level, then
executes the DROPN. Thus, 4 DROPN and 4 ENTER
DROPN have the same effect. |
| DUPDUP |
The same DUP DUP, that is, the same as pressing DUP
twice. |
| NIP |
Drops the item in level 2 of the stack and moves anything
above level 2 down one level. |
| NDUPN |
With an integer n in the command line, NDUPN puts n
copies of the item on level 1 into levels 2 through n + 1, and
n is put on level 1. Everything else on the stack is moved
up n levels. If the command line is empty and there is an
integer n on level 1, NDUPN removes n, drops everything
on the stack down one level, then executes NDUPN. Thus,
3 NDUPN and 3 ENTER NDUPN have the same effect. |
Suppose the bowling league of Section 1 computes a bowler's handicap for the next week as 80% of (200 minus this week's
average). Let's write a program to take three scores from the stack and leave the total on level 3, the average truncated to
an integer on level 2, and next week's handicap truncated to an integer on level 1.
Type this program into your calculator and store it as BWL2 then try it with several sets of data. With 172, 177 and 186,
the output should be 535 on level 3, 178 on level 2, and 17 on level 1. Notice that the commands 0 MAX are needed to
make sure that a bowler whose average is over 200 will not have a negative handicap. The FLOOR function (LS MTH F5-REAL NXT NXT F3-FLOOR) is described on page 3-14 of UG.
EXERCISE SET 2
1. Change Problem 3 of Exercise Set 1 so that the distance is left on level 2 of the stack and the time on level 1. Save this
new version as TMR2.
2. Change Problem 1 of Exercise Set 1 so that the original amount is left on level 3 of the stack, the tax on level 2, and the
total on level 1. Call this new version TAX2.
3. Write a program called LIN1 to do linear interpolation. That is, given the two points (x1, y1), (x2, y2) and a number x
between x1 and x2, find  The program should begin with x1 in level 5, y1 in level 4, x2 in level 3,
y2 in level 2, and x in level 1; and should end with y in level 1 and the rest of the stack empty. (First strive for a solution
which works, but then try to do it in as few steps as possible.)
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