Texas Instruments TI89 Developer Guide - Page 772
is_nonnegative, is0, is_real
UPC - 033317198566
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730 Appendix A: System Routines - Logic is_never0 Declaration: Boolean is_never0 (EStackIndex i) Category(ies): Logic Description: Determines whether the internally-simplified algebraic expression indexed by i is nonzero (possibly unreal) for all finite values of all variables therein. 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 nonzero (possibly unreal) for all finite values of all variables therein. Otherwise returns FALSE, even though expression i might always be nonzero. Assumptions: None Side Effects: None Availability: On AMS 2.02 and higher. TI-89 / TI-92 Plus Differences: None See Also: is_nonnegative, is_positive, is_nonpositive, is0, is_negative, is_real Example: void push_maybe0_factors (EStackIndex i) /* i initially indexes a term (that might recur to a sum). Pushes the product of the factors of i that might be zero. */ { if (IS_NUMBER_TAG (ESTACK (i))) push_expression (Integer1Index); else { push_maybe0_factors (remaining_factors_index (i)); i = lead_factor_index (i); if (is_never0 (i) && (EXPONENTIATION_TAG != ESTACK (i) || is_nonnegative (POWER_EXPONENT_INDEX (i)) || is_never0 (POWER_BASE_INDEX (i)) ) ) ; else times_top (i); } } /* end push_maybe0_factors */ TI-89 / TI-92 Plus Developer Guide Not for Distribution Beta Version January 26, 2001