X-Git-Url: https://ginac.de/ginac.git//ginac.git?a=blobdiff_plain;f=ginac%2Futils.cpp;h=6935bcd8e1a71fc93b436efc96b4fb8aa09ea2dd;hb=b16d5b34f40c9dcd6bd4f9e1fdeeb65cb1612db3;hp=1900e1b30ca20188eceb3d78b6e6dbed718493e1;hpb=761d1597532504762c1f9b438c7727c4f74d7da3;p=ginac.git

diff --git a/ginac/utils.cpp b/ginac/utils.cpp
index 1900e1b3..6935bcd8 100644
--- a/ginac/utils.cpp
+++ b/ginac/utils.cpp
@@ -4,7 +4,7 @@
  *  but not of any interest to the user of the library. */
 
 /*
- *  GiNaC Copyright (C) 1999-2017 Johannes Gutenberg University Mainz, Germany
+ *  GiNaC Copyright (C) 1999-2019 Johannes Gutenberg University Mainz, Germany
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -53,6 +53,19 @@ unsigned log2(unsigned n)
 	return k;
 }
 
+/** Compute the multinomial coefficient n!/(p1!*p2!*...*pk!) where
+ *  n = p1+p2+...+pk, i.e. p is a partition of n.
+ */
+const numeric
+multinomial_coefficient(const std::vector<unsigned> & p)
+{
+	numeric n = 0, d = 1;
+	for (auto & it : p) {
+		n = n.add(numeric(it));
+		d = d.mul(factorial(numeric(it)));
+	}
+	return factorial(n).div(d);
+}
 
 //////////
 // flyweight chest of numbers is initialized here: