[GiNaC-devel] [PATCH 3/4] Added `degree_vector' utility function.

[Alexei Sheplyakov]

It's a generalization of degree(expr, var) for multivariate polynomials.
---
 ginac/polynomial/collect_vargs.cpp |   12 ++++++++++++
 ginac/polynomial/collect_vargs.h   |   31 +++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/ginac/polynomial/collect_vargs.cpp b/ginac/polynomial/collect_vargs.cpp
index 2593268..c4368fb 100644
--- a/ginac/polynomial/collect_vargs.cpp
+++ b/ginac/polynomial/collect_vargs.cpp
@@ -177,6 +177,18 @@ ex lcoeff_wrt(ex e, const exvector& x)
 	return ec.rbegin()->second;
 }
 
+exp_vector_t degree_vector(ex e, const exvector& vars)
+{
+	e = e.expand();
+	exp_vector_t dvec(vars.size());
+	for (std::size_t i = vars.size(); i-- != 0; ) {
+		const int deg_i = e.degree(vars[i]);
+		e = e.coeff(vars[i], deg_i);
+		dvec[i] = deg_i;
+	}
+	return dvec;
+}
+
 cln::cl_I integer_lcoeff(const ex& e, const exvector& vars)
 {
 	ex_collect_t ec;
diff --git a/ginac/polynomial/collect_vargs.h b/ginac/polynomial/collect_vargs.h
index 44c3d72..a927c3f 100644
--- a/ginac/polynomial/collect_vargs.h
+++ b/ginac/polynomial/collect_vargs.h
@@ -28,10 +28,34 @@
 #include <cln/integer.h>
 #include <utility> // for std::pair
 #include <vector>
+#include <algorithm> // std::lexicographical_compare
 
 namespace GiNaC {
 
 typedef std::vector<int> exp_vector_t;
+
+static inline bool operator<(const exp_vector_t& v1, const exp_vector_t& v2)
+{
+	return std::lexicographical_compare(v1.rbegin(), v1.rend(),
+					    v2.rbegin(), v2.rend());
+}
+
+static inline bool operator>(const exp_vector_t& v1, const exp_vector_t& v2)
+{
+	if (v1 == v2)
+		return false;
+	return !(v1 < v2);
+}
+
+static inline bool zerop(const exp_vector_t& v)
+{
+	for (exp_vector_t::const_reverse_iterator i = v.rbegin(); i != v.rend(); ++i) {
+		if (*i != 0) 
+			return false;
+	}
+	return true;
+}
+
 typedef std::vector<std::pair<exp_vector_t, ex> > ex_collect_t;
 
 extern void
@@ -46,6 +70,13 @@ ex_collect_to_ex(const ex_collect_t& ec, const exvector& x);
  */
 extern ex lcoeff_wrt(ex e, const exvector& x);
 
+
+/**
+ * Degree vector of a leading term of a multivariate polynomial.
+ * (generalization of degree(expr, var))
+ */
+extern exp_vector_t degree_vector(ex e, const exvector& vars);
+
 /**
  * Leading coefficient c \in R (where R = Z or Z_p) of a multivariate
  * polynomial e \in R[x_0, \ldots, x_n]
-- 
1.7.1