+__isl_give struct isl_upoly *isl_upoly_pow(isl_ctx *ctx, int pos, int power)
+{
+ int i;
+ struct isl_upoly *up;
+ struct isl_upoly_rec *rec;
+ struct isl_upoly_cst *cst;
+
+ rec = isl_upoly_alloc_rec(ctx, pos, 1 + power);
+ if (!rec)
+ return NULL;
+ for (i = 0; i < 1 + power; ++i) {
+ rec->p[i] = isl_upoly_zero(ctx);
+ if (!rec->p[i])
+ goto error;
+ rec->n++;
+ }
+ cst = isl_upoly_as_cst(rec->p[power]);
+ isl_int_set_si(cst->n, 1);
+
+ return &rec->up;
+error:
+ isl_upoly_free(&rec->up);
+ return NULL;
+}
+
+/* r array maps original positions to new positions.
+ */
+static __isl_give struct isl_upoly *reorder(__isl_take struct isl_upoly *up,
+ int *r)
+{
+ int i;
+ struct isl_upoly_rec *rec;
+ struct isl_upoly *base;
+ struct isl_upoly *res;
+
+ if (isl_upoly_is_cst(up))
+ return up;
+
+ rec = isl_upoly_as_rec(up);
+ if (!rec)
+ goto error;
+
+ isl_assert(up->ctx, rec->n >= 1, goto error);
+
+ base = isl_upoly_pow(up->ctx, r[up->var], 1);
+ res = reorder(isl_upoly_copy(rec->p[rec->n - 1]), r);
+
+ for (i = rec->n - 2; i >= 0; --i) {
+ res = isl_upoly_mul(res, isl_upoly_copy(base));
+ res = isl_upoly_sum(res, reorder(isl_upoly_copy(rec->p[i]), r));
+ }
+
+ isl_upoly_free(base);
+ isl_upoly_free(up);
+
+ return res;
+error:
+ isl_upoly_free(up);
+ return NULL;
+}
+