187 lines
2.3 KiB
C++
187 lines
2.3 KiB
C++
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#include "stdafx.h"
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//-----------------------------------------------------------------------------
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//
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// Absolute value function
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//
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// A number of things are done to produce a canonical form:
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//
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// abs(-a) -> abs(a)
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//
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// abs(b - a) -> abs(a - b)
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//
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//-----------------------------------------------------------------------------
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#include "defs.h"
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extern void conjugate(void);
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extern int isnegativeterm(U *);
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static void absval2(void);
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static void absval_tensor(void);
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static int iscomplexnumber(U *);
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// to here from the evaluator
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void
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eval_abs(void)
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{
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push(cadr(p1));
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eval();
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absval();
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}
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void
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absval(void)
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{
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save();
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absval2();
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restore();
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}
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static void
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absval2(void)
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{
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p1 = pop();
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if (p1->k == TENSOR) {
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absval_tensor();
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return;
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}
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if (isnum(p1)) {
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push(p1);
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if (isnegativenumber(p1))
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negate();
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return;
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}
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if (iscomplexnumber(p1)) {
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push(p1);
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push(p1);
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conjugate();
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multiply();
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push_rational(1, 2);
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power();
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return;
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}
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if (isnegativeterm(p1) || (car(p1) == symbol(ADD) && isnegativeterm(cadr(p1)))) {
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push(p1);
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negate();
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p1 = pop();
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}
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push_symbol(ABS);
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push(p1);
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list(2);
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}
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static void
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absval_tensor(void)
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{
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if (p1->u.tensor->ndim != 1)
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stop("abs(tensor) with tensor rank > 1");
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push(p1);
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push(p1);
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conjugate();
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inner();
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push_rational(1, 2);
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power();
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}
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// returns 1 if there's a symbol somewhere
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static int
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issymbolic(U *p)
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{
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if (p->k == SYM)
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return 1;
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if (iscons(p)) {
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while (iscons(p)) {
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if (issymbolic(car(p)))
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return 1;
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p = cdr(p);
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}
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}
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return 0;
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}
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// returns 1 if there's -1 to a power somewhere
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static int
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iscomplex(U *p)
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{
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if (car(p) == symbol(POWER) && isminusone(cadr(p)))
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return 1;
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if (iscons(p)) {
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while (iscons(p)) {
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if (iscomplex(car(p)))
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return 1;
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p = cdr(p);
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}
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}
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return 0;
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}
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static int
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iscomplexnumber(U *p)
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{
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if (iscomplex(p) && !issymbolic(p))
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return 1;
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else
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return 0;
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}
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static char *s[] = {
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"abs(2)",
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"2",
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"abs(2.0)",
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"2",
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"abs(-2)",
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"2",
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"abs(-2.0)",
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"2",
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"abs(a)",
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"abs(a)",
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"abs(-a)",
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"abs(a)",
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"abs(2*a)",
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"abs(2*a)",
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"abs(-2*a)",
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"abs(2*a)",
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"abs(2.0*a)",
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"abs(2*a)",
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"abs(-2.0*a)",
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"abs(2*a)",
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"abs(a-b)+abs(b-a)",
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"2*abs(a-b)",
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"abs(3 + 4 i)",
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"5",
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"abs((2,3,4))",
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"29^(1/2)",
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};
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void
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test_abs(void)
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{
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test(__FILE__, s, sizeof s / sizeof (char *));
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}
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