Texas Instruments TI-89 - Is_Nonpositive

732
Appendix A: System Routines — Logic
TI
-
89 / TI
-
92 Plus Developer Guide
Not for Distribution
Beta Version January 26, 2001
is_nonpositive
Declaration:
Boolean
is_nonpositive
(EStackIndex
i
)
Category(ies):
Logic
Description:
Determines whether the internally-simplified algebraic expression indexed
by
i
is real and <= 0 for all finite values of all variables therein. Takes into
account bounds indexed by
NG_such_that_index
.
L
0 and
L
0.0 are NOT
considered nonpositive.
Inputs:
i
— Index of the top tag of an internally-simplified expression.
Outputs:
Returns TRUE if it can determine that the internally-simplified algebraic
expression indexed by
i
is real and <= 0 for all finite values of all variables
therein. Otherwise returns FALSE, even though the expression indexed by
i
might always be nonpositive.
Assumptions:
None
Side Effects:
None
Availability:
On AMS 2.02 and higher.
TI
-
89 / TI
-
92 Plus
Differences:
None
See Also: is_never0, is_positive, is_nonnegative, is0, is_negative, is_real
Example:
Boolean have_same_sign (EStackIndex i, EStackIndex j)
/* Returns TRUE if the expressions indexed by i and j are both non-negative
or both nonpositive.
*/
{ return is_nonnegative (i) && is_nonnegative (j) ||
is_nonpositive (i) && is_nonpositive (j);
}