Appendix A: System Routines — Lists and Matrices
699
TI
-
89 / TI
-
92 Plus Developer Guide
Not for Distribution
Beta Version January 26, 2001
push_median
(continued)
Example:
This example pushes a list on the estack that corresponds to the median
for the input list. For each element in the input list the element in the output
list is a negative one if the element is less than the median, a zero if it is
equal to the median, and a positive one if it greater than the median. Note
that since the output list is created in reverse order on the estack,
push_reversed_tail
is used to reverse the order of the list back to normal.
const BYTE INT_NEG1[] = {END_TAG,1,1,NEGATIVE_INTEGER_TAG};
const BYTE INT_0[] = {END_TAG,0,NONNEGATIVE_INTEGER_TAG};
const BYTE INT_1[] = {END_TAG,1,1,NONNEGATIVE_INTEGER_TAG};
EStackIndex old_top, idx, median_idx, cond_idx;
old_top = top_estack;
push_quantum(END_TAG);
push_Float(-5.0);
push_Float(1.0);
push_Float(2.0);
push_Float(4.0);
push_Float(99.0);
idx = top_estack;
push_quantum(LIST_TAG);
push_median( idx+1 );
median_idx = top_estack;
push_quantum( END_TAG );
while (END_TAG != ESTACK(idx)) {
push_difference( median_idx, idx );
if (is0(top_estack))
cond_idx = (EStackIndex) INT_0+2;
else if (is_positive(top_estack))
cond_idx = (EStackIndex) INT_1+3;
else
cond_idx = (EStackIndex) INT_NEG1+3;
delete_expression( top_estack );
push_expression( cond_idx );
idx = next_expression_index( idx );
}
idx = top_estack;
push_reversed_tail( idx );
delete_between ( old_top, idx );
push_quantum( LIST_TAG );
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