X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=blobdiff_plain;f=ginac%2Fpseries.cpp;h=87d0e4377a6ccbb3023723759b5c6be3773b45d8;hp=4491915841b1cd746d32cde71c8effc395257d4c;hb=6564c3b961f7e0b69c20187b56f90d86d4fdcb9a;hpb=f4ea690a3f118bf364190f0ef3c3f6d2ccdf6206

diff --git a/ginac/pseries.cpp b/ginac/pseries.cpp
index 44919158..87d0e437 100644
--- a/ginac/pseries.cpp
+++ b/ginac/pseries.cpp
@@ -242,16 +242,30 @@ int pseries::ldegree(const symbol &s) const
 ex pseries::coeff(const symbol &s, int n) const
 {
     if (var.is_equal(s)) {
-        epvector::const_iterator it = seq.begin(), itend = seq.end();
-        while (it != itend) {
-            int pow = ex_to_numeric(it->coeff).to_int();
-            if (pow == n)
-                return it->rest;
-            if (pow > n)
-                return _ex0();
-            it++;
-        }
-        return _ex0();
+		if (seq.size() == 0)
+			return _ex0();
+
+		// Binary search in sequence for given power
+		numeric looking_for = numeric(n);
+		int lo = 0, hi = seq.size() - 1;
+		while (lo <= hi) {
+			int mid = (lo + hi) / 2;
+			GINAC_ASSERT(is_ex_exactly_of_type(seq[mid].coeff, numeric));
+			int cmp = ex_to_numeric(seq[mid].coeff).compare(looking_for);
+			switch (cmp) {
+				case -1:
+					lo = mid + 1;
+					break;
+				case 0:
+					return seq[mid].rest;
+				case 1:
+					hi = mid - 1;
+					break;
+				default:
+					throw(std::logic_error("pseries::coeff: compare() didn't return -1, 0 or 1"));
+			}
+		}
+		return _ex0();
     } else
         return convert_to_poly().coeff(s, n);
 }