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[qfcc] Implement mutli-vector division

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But only for scalar divisors. The simple method of AB†/(BB†) works only
if B is a versor and there's also the problem of left and right
division. Thanks to sudgy for making me stop and think before I actually
implemented anything (though he mentioned only that it doesn't work for
general mutli-vector divisors).
This commit is contained in:
Bill Currie 2023-08-28 12:15:45 +09:00
parent 41e0483102
commit 6b1684b711
2 changed files with 42 additions and 1 deletions
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32
tools/qfcc/source/expr_algebra.c
View file

@ -1374,7 +1374,37 @@ commutator_product (expr_t *e1, expr_t *e2)
static expr_t *
multivector_divide (expr_t *e1, expr_t *e2)
{
internal_error (e1, "not implemented");
if (is_algebra (get_type (e2))) {
return error (e2, "Division is left-right ambiguous (and works only"
" for versors anyway). Use explicit reversion and divide"
" by square magnitude instead.");
}
if (!is_algebra (get_type (e1))) {
internal_error (e1, "wtw?");
}
auto t1 = get_type (e1);
auto algebra = algebra_get (t1);
auto layout = &algebra->layout;
auto stype = algebra->type;
expr_t *a[layout->count] = {};
e1 = mvec_expr (e1, algebra);
e2 = promote_scalar (algebra->type, e2);
mvec_scatter (a, e1, algebra);
for (int i = 0; i < layout->count; i++) {
if (!a[i]) {
continue;
}
auto den = e2;
auto ct = get_type (a[i]);
int width = type_width (ct);
if (width > 1) {
den = new_extend_expr (den, vector_type (stype, width), 2, false);
}
a[i] = new_binary_expr ('/', a[i], den);
a[i]->e.expr.type = ct;
}
return mvec_gather (a, algebra);
}
expr_t *

11
tools/qfcc/test/pga2d.r
View file

@ -230,5 +230,16 @@ main (void)
s.scalar, s.bvec);
return 1;
}
e.mvec = e.mvec / 2; // odd
if ((dvec3)e.vec != '2 3 0.5'd || (scalar_t)e.tvec != -10) {
printf ("odd† != '2 3 0.5' + -10: %lv %g\n", e.vec, e.tvec);
return 1;
}
s.mvec = s.mvec / 2; // even
if (s.scalar != -4.5 || (dvec3)s.bvec != '-7 -22 -23'd) {
printf ("even† != -4.5, '-7 -22 -23': %g %lv\n",
s.scalar, s.bvec);
return 1;
}
return 0; // to survive and prevail :)
}