build: accept both python 3 and python 2

[ginac.git] / ginac / indexed.cpp

diff --git a/ginac/indexed.cpp b/ginac/indexed.cpp
index 86af6811ba3752edb7caa3e174357acb3caff593..cf52f4429c672d6287123d2f8f556ecb3d477935 100644 (file)
--- a/ginac/indexed.cpp
+++ b/ginac/indexed.cpp
@@ -3,7 +3,7 @@
  *  Implementation of GiNaC's indexed expressions. */
 
 /*
- *  GiNaC Copyright (C) 1999-2016 Johannes Gutenberg University Mainz, Germany
+ *  GiNaC Copyright (C) 1999-2020 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
@@ -394,7 +394,7 @@ ex indexed::derivative(const symbol & s) const
 // global functions
 //////////
 
-struct idx_is_equal_ignore_dim : public std::binary_function<ex, ex, bool> {
+struct idx_is_equal_ignore_dim {
        bool operator() (const ex &lh, const ex &rh) const
        {
                if (lh.is_equal(rh))
@@ -506,7 +506,7 @@ exvector ncmul::get_free_indices() const
        return free_indices;
 }
 
-struct is_summation_idx : public std::unary_function<ex, bool> {
+struct is_summation_idx {
        bool operator()(const ex & e)
        {
                return is_dummy_pair(e, e);
@@ -719,7 +719,7 @@ next_index: ;
 }
 
 /* Ordering that only compares the base expressions of indexed objects. */
-struct ex_base_is_less : public std::binary_function<ex, ex, bool> {
+struct ex_base_is_less {
        bool operator() (const ex &lh, const ex &rh) const
        {
                return (is_a<indexed>(lh) ? lh.op(0) : lh).compare(is_a<indexed>(rh) ? rh.op(0) : rh) < 0;