**HP Prime: The EXECON Command Tutorial**

**The EXECON Command**

The EXECON creates a new list based on the elements in one
or more lists by given an operation. You
can create any expression. The list
returned may or may not be the same length of the original lists.

The general syntax is:

EXECON( expression, list 1, [list 2], [list 3], …)

You can use more than one list. The expression is set in
quotes. To use the list elements, call
up the ampersand (&). Call up the
ampersand symbol by pressing [ Shift ], [ 9 ] (and choose the ampersand). Example expressions include “&1+&2”
and “&1^3”.

On this tutorial we will use EXECON for specific
situations.

Calling the EXECON Command

You can call the EXECON command from the Catalog or in the
Programming editing mode by selecting (Cmds), 7 for More, 8 for EXECON (version
10077).

For the tutorial set L1 and L2 as:

L1 = {1, 2, 3, 4, 5}

L2 = {2, 4, 6, 8, 10}

Situation 1: Operate
on each member of a list.

Your expression string will contain &1 any time you want
to reference the list. EXECON executes
the function f(&1, any constants).
As a reminder, you can get the ampersand symbol by pressing [ Shift ],
9, and then selecting it from the character table.

Example 1: Take the
cube of each element of L1.

Syntax: EXECON(“&1^3”,
L1)

Results: {1, 8, 27,
64, 125}

Example 2: Apply the function
2*e^x – x to each element of L1.

Syntax: EXECON(“2*e^(&1)-&1”,L1)

Results (to 5 decimal places): {4.43656, 12.77811, 37.17107,
105.19638, 291.82632}

Situation 2: Operate
a function for two lists, element by element.

Include &1 for the first list and &2 for the second
list. This is going to the resulting
list:

{ f(&1(1), &2(1)),
f(&1(2), &2(2)),
f(&1(3), &2(3)), … , f(&1(n), &2(n)) }

You can extend this to three lists or more by adding &3,
&4, etc… up to nine lists.

The order of arguments are important.

EXECON(“&1/&2”, L1, L2) returns {0.5, 0.5, 0.5, 0.5,
0.5}

EXECON(“&1/&2”, L2, L1) returns {2, 2, 2, 2, 2}

Situation 3:
Condensing a List by operating on two or more elements.

Here we are going to use one list. To execute an operation on two consecutive
elements, use &1 and &2.
Remember, we are only using one list.
In this context, &1 and &2 represent neighboring elements. Hence:

Input: {a1, a2, a3,
a4, …. , a_n-2, a_n-1, a_n}

Output: { f(a1, a2),
f(a2, a3), f(a3, a4), … , f(a_n-2, a_n-1), f(a_n-1, a_n)}

Example: EXECON(“&1*&2”,
L1) returns {2, 6, 12, 20}

To execute an operation for elements two apart, use &1
and &3.

Input: {a1, a2, a3,
a4, …. , a_n-2, a_n-1, a_n}

Output: { f(a1, a3),
f(a2, a4), f(a3, a5), … , f(a_n-2, a_n)}

Example: EXECON(“&1*&3”,
L1) returns {3, 8, 15}

If you want to execute an operation on three consecutive
elements, use &1, &2, and &3.

Input: {a1, a2, a3,
a4, …. , a_n-2, a_n-1, a_n}

Output: { f(a1, a2,
a3), f(a2, a3, a4), … , f(a_n-2, a_n-1,
a_n) }

Example: EXECON(“&1*&2*&3”,
L1) returns {6, 24, 60}

Situation 4: Starting
at specific position of the list. (up to
9 lists, to the start point of the 9

^{th}element)
To start at a specific element later in the list, use the
syntax &mn, the mth list, the nth
element.

Example 1:

EXECON(“&13 + &2”, L1, L2) will operate on the
following elements: {3, 4, 5} from L1
(starting at the 3

^{rd}element) and {2, 4, 6} from L2. The result will be {5, 8, 11}.
Example 2:

EXECON(“&1 * &22”, L1, L2) will operate on the following
elements: {1, 2, 3, 4} from L1 and {4,
6, 8, 10} from L2 (starting from the 2

^{nd}element). The result is {4, 12, 24, 40}.
Please refer to the illustration below.

This is a basic demonstration of EXECON. I hope you found this tutorial useful. Until next time,

Eddie

This blog is property of Edward Shore, 2016.