+void
+add(...)
+PROTOTYPE: @
+PREINIT:
+ HV *res;
+ SV *cur, *val;
+ HE *key, *old;
+ I32 i;
+CODE:
+ if (!items)
+ XSRETURN_UNDEF;
+ res = newHV();
+ for (i = 0; i < items; ++i) {
+ cur = ST(i);
+ if (!SvOK(cur))
+ continue;
+ if (!SvROK(cur)) {
+ NV v = 1;
+ if ((old = hv_fetch_ent(res, cur, 1, 0)) && SvOK(val = HeVAL(old)))
+ v += SvNV(val);
+ sn_store_ent(res, cur, newSVnv(v), 0);
+ continue;
+ }
+ cur = SvRV(cur);
+ hv_iterinit((HV *) cur);
+ while (key = hv_iternext((HV *) cur)) {
+ SV *k = HeSVKEY_force(key);
+ NV v = SvNV(HeVAL(key));
+ if ((old = hv_fetch_ent(res, k, 1, 0)) && SvOK(val = HeVAL(old)))
+ v += SvNV(val);
+ sn_store_ent(res, k, newSVnv(v), 0);
+ }
+ }
+ if (!hv_iterinit(res)) {
+ SvREFCNT_dec(res);
+ XSRETURN_UNDEF;
+ }
+ ST(0) = sv_2mortal(newRV_noinc((SV *) res));
+ XSRETURN(1);
+
+void
+cumulate(SV *sv, SV *nsv, SV *csv)
+PROTOTYPE: $$$
+PREINIT:
+ HV *res;
+ HE *key;
+ NV c0, c, a;
+ UV i, n;
+CODE:
+ if (!SvOK(sv))
+ XSRETURN_UNDEF;
+ n = SvUV(nsv);
+ c0 = SvNV(csv);
+ if (!n) {
+ ST(0) = sv_2mortal(newSVuv(0));
+ XSRETURN(1);
+ }
+ if (!SvROK(sv) || !c0) {
+ ST(0) = sv;
+ XSRETURN(1);
+ }
+ sv = SvRV(sv);
+ if (!hv_iterinit((HV *) sv))
+ XSRETURN_UNDEF;
+ if (c0 == 1 || (SvIOK(csv) && SvIV(csv) == 1)) {
+ c = n;
+ } else {
+ c = 1;
+ a = c0;
+ for (; n > 0; n /= 2) {
+ if (n % 2)
+ c *= a;
+ a *= a;
+ }
+ c = (1 - c) / (1 - c0);
+ }
+ res = newHV();
+ while (key = hv_iternext((HV *) sv)) {
+ SV *k = HeSVKEY_force(key);
+ SV *val = newSVnv(c * SvNV(HeVAL(key)));
+ sn_store_ent(res, k, val, 0);
+ }
+ ST(0) = sv_2mortal(newRV_noinc((SV *) res));
+ XSRETURN(1);
+