Texas Instruments TI89 Developer Guide - Page 773
is_never0, is_positive, is0, is_real
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Appendix A: System Routines - Logic 731 is_nonnegative Declaration: Boolean is_nonnegative (EStackIndex i) Category(ies): Logic Description: Determines whether the internally-simplified algebraic expression indexed by i is non-negative real for all finite values of all variables therein. Takes into account bounds indexed by NG_such_that_index. ALL zeros are considered non-negative, even L0 and L0.0 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 non-negative real for all finite values of all variables therein. Otherwise returns FALSE, even though the expression indexed by i might always be non-negative. 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_nonpositive, is0, is_negative, is_real Example: EStackIndex index_nonnegative_factor (EStackIndex i) /* i indexes a term. Returns NULL_INDEX if it cannot determine that one of its explicit factors is non-negative. Otherwise returns i or the index of its first remaining factors for which the lead factor has been determined to be nonnegative. */ { while (! is1 (i)) if (is_nonnegative (lead_factor_index (i))) return i; else i = remaining_factors_index (i); return NULL_INDEX; } TI-89 / TI-92 Plus Developer Guide Not for Distribution Beta Version January 26, 2001
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