Texas Instruments TI-89 - Push_Lim

794
Appendix A: System Routines — Math
TI
-
89 / TI
-
92 Plus Developer Guide
Not for Distribution
Beta Version January 26, 2001
push_lim
Declaration:
void
push_lim
(EStackIndex
i
, EStackIndex
ki
, EStackIndex
j
,
EStackIndex
direction
)
Category(ies):
Math
Description:
Pushes the limit of expression
i
, as variable
ki
approaches expression
j.
Subject to overriding for consistency with a signed zero or infinity for point
j
,
the limit is from the right if the expression indexed by
direction
is positive,
versus from the left if negative, or from both directions otherwise. If invoked
via
push_internal_simplify
,
ki
and
i
are simplified to deepest variable.
Moreover, the simplification of
i
and the computation of the limit are done in
the context of a “such that” constraining
ki
to a small (but finite)
neighborhood of point
j
, from the direction(s) specified by direction.
Inputs:
i
— Indexes the top tag of an internally-simplified algebraic
expression, algebraic comparison, or aggregate thereof.
ki
— Indexes the top tag of a variable.
j
,
direction
— Indexes to internally-simplified algebraic expressions.
Outputs:
None
Assumptions:
None
Side Effects:
None
Availability:
On AMS 2.02 and higher.
TI
-
89 / TI
-
92 Plus
Differences:
None
See Also: push_substitute_simplify, push_subst_no_simp
Example:
void push_subst_or_lim (EStackIndex i, EStackIndex ki, EStackIndex j)
/* Pushes the result of substituting j for ki in i, unless it yields a
nonunique result and the two-sided limit does not, in which case it
pushes the latter instead.
*/
{ Access_AMS_Global_Variables;
EStackIndex k, old_top = top_estack;
push_substitute_simplify (i, ki, j);
k = top_estack;
if (is_undefined (k))
{ push_lim (i, ki, j, Integer0Index);
if (is_undefined (top_estack))
top_estack = k;
else delete_between (old_top, k);
}
} /* end push_subst_or_lim */