Texas Instruments TI89 Developer Guide - Page 1163
Variable Name Utilities, Algebra Utilities, is_complex_number, is_constant
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Appendix A: System Routines - Variable Name Utilities 1121 is_variable Declaration: Boolean is_variable (EStackIndex i) Category(ies): Variable Name Utilities, Algebra Utilities Description: Determines whether i indexes a subscripted or unsubscripted variable. Inputs: i - Index of the top tag of an internally-simplified expression. Outputs: Returns TRUE if i indexes a subscripted or unsubscripted variable. Assumptions: None Side Effects: None Availability: On AMS 2.00 and higher. TI-89 / TI-92 Plus Differences: None See Also: is_complex_number, is_constant Example: Boolean is_rational_expression (EStackIndex i) /* i indexes an expression. Returns TRUE if it is a rational expression in all of its variables. Otherwise returns FALSE. */ { EStackIndex j; for (;;) if (IS_NUMBER_OR_VARIABLE_TAG (ESTACK (i)) || is_variable (i)) return TRUE; else if (ADD_TAG == ESTACK (i) || MULTIPLY_TAG == ESTACK (i)) if (is_rational_expression (--i)) i = next_expression_index (i); else return FALSE; else if (EXPONENTIATION_TAG == ESTACK (i)) { j = next_expression_index (--i); if (! IS_INTEGER_TAG (ESTACK (j))) return is_constant (i); } else return is_constant (i); } TI-89 / TI-92 Plus Developer Guide Not for Distribution Beta Version January 26, 2001
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