Texas Instruments TI-89 Developer's Guide

294
Appendix A: System Routines — Algebra Utilities
TI
-
89 / TI
-
92 Plus Developer Guide
Not for Distribution
Beta Version January 26, 2001
reductum_index
Declaration:
EStackIndex
reductum_index
(EStackIndex
i
)
Category(ies):
Algebra Utilities
Description:
If
i
indexes an ADD_TAG, returns the index of the deeper of its two
operands. Otherwise returns Float0Index if IS_ARITH_APPROX is true and
Integer0Index if IS_ARITH_APPROX is false. Internally-simplified
expressions have the most main term shallowest.
For example:
If i indexes the internally-simplified expression
2 + x + y
then
reductum_index
(i) returns index(y + 2).
If i indexes the internally-simplified expression (
2
)
then
reductum_index
(i) returns Float0Index if IS_ARITH_APPROX is true
and Integer0Index if IS_ARITH_APPROX is false.
Note that Float0Index and Integer0Index are not ordinarily physically within
the expression indexed by
i
.
For the default mode IS_RECURSIVE, similar powers of the main variable
are collected.
For example:
If i indexes the internally-simplified expression
x^2 * y + x^2 + 5)
then
reductum_index
(i) returns index(5).
Internally-simplified differences are represented as sums with negated
subtrahends.
For example:
If i indexes the internally-simplified expression
x
L
y
then
reductum_index
(i) returns index(y
†
(
L
1)).
Inputs:
i
— Indexes the top tag of an expression.
Outputs:
If
i
indexes an ADD_TAG, returns the index of the deeper of its two
operands. Otherwise returns Float0Index if IS_ARITH_APPROX is true and
Integer0Index if IS_ARITH_APPROX is false.
Assumptions:
None
Side Effects:
None
(continued)

Texas Instruments TI-89 Specifications

General

Display size (HxV)	100 x 160 mm
Memory type	639K FLASH ROM, 188K bytes RAM
Compatible operating systems	Operating System 2.09
Battery type	AAA