HP 48gII Graphing manual Exco Expand and Collect Completely, Techniques used in Exco, `Oexco K

EXCO (Expand and Collect Completely)

EXCO repeatedly executes EXPAN on an algebraic until the algebraic doesn’t change, then repeatedly executes COLCT until the algebraic doesn’t change. In some cases the result will be a number.

Expressions with many products of sums or with powers can take many iterations of EXPAN to expand completely, resulting in a long execution time for EXCO.

Level 1	→	Level 1
'algebraic'	→	'algebraic'
'algebraic'	→	z

Techniques used in EXCO

Subroutines. EXCO calls the program MULTI twice. It is more efficient to create program MULTI and simply call its name twice than write each step in MULTI two times.

Required Programs

MULTI (Multiple Execution) repeatedly executes the programs that EXCO provides as arguments.

EXCO program listing
		Program:	Comments:
		«
		« EXPAN »	Puts a program on the stack as
			the level 1 argument for MULTI.
			The program executes the
			EXPAN command.
		MULTI	Executes EXPAN until the
			algebraic object doesn’t change.
		« COLCT »	Puts another program on the
			stack for MULTI. The program
			executes the COLCT command.
		MULTI	Executes COLCT until the
			algebraic object doesn’t change.
		»
		`OEXCO K	Stores the program in EXCO.
Checksum: # 41162d
Bytes:	65.5

Example: Expand and collect completely the expression:

3x(4y+z) +(8x–5z)2

Enter the expression.

O3 * X *

RPL Programming Examples 215