Add operator[] to placeholders

test/subscript.cpp

@@ -0,0 +1,27 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/lambda2.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <functional>
+
+int main()
+{
+    using namespace boost::lambda2;
+
+    int x[] = { 1, 2, 3, 4 };
+
+    BOOST_TEST_EQ( _1[0](x), x[0] );
+    BOOST_TEST_EQ( _1[_2](x, 1), x[1] );
+    BOOST_TEST_EQ( (_1[_2] + _3[_4])(x, 2, x, 3), x[2] + x[3] );
+    BOOST_TEST_EQ( std::bind(_1 + _2, _1[_2], _3[_4])(x, 2, x, 3), x[2] + x[3] );
+
+    _1[0](x) = 7;
+    BOOST_TEST_EQ( x[0], 7 );
+
+    _1[_2](x, 1) = 8;
+    BOOST_TEST_EQ( x[1], 8 );
+
+    return boost::report_errors();
+}