Is_Positive - Texas Instruments TI-89 Developer's Manual

Appendix A: System Routines — Logic

is_positive

Declaration: Boolean is_positive (EStackIndex i )
Category(ies): Logic
Description: Determine whether the internally-simplified algebraic expression indexed
by i is positive real for all finite values of all variables therein. Takes into
account bounds indexed by NG_such_that_index. +0 and +0.0 are NOT
considered positive.
Inputs: i
Outputs: Returns TRUE if it can determine that the internally-simplified algebraic
expression indexed by i is positive real for all finite values of all variables
therein. Otherwise returns FALSE, even though the expression indexed by
i might always be positive.
Assumptions: None
Side Effects: None
Availability: On AMS 2.02 and higher.
TI-89 / TI-92 Plus
Differences: None
See Also: is_never0, is_nonpositive, is_nonnegative, is0, is_negative, is_real
Example:
int gt0_le0_unknown (EStackIndex i)
/* i indexes a nonzero expression.
Returns 1 if it determines that the expression is > 0, else -1 if <= 0, else 0.
*/
{ return is_positive (i) ? 1 : -is_nonpositive (i);
}
TI-89 / TI-92 Plus Developer Guide
— Index of the top tag of an internally-simplified expression.
Not for Distribution
733
Beta Version January 26, 2001