Add minimal support for Array<string>, and fix Tensor<string>

Eigen/src/Core/NumTraits.h

@@ -234,6 +234,27 @@ struct NumTraits<Array<Scalar, Rows, Cols, Options, MaxRows, MaxCols> >
   static inline RealScalar dummy_precision() { return NumTraits<RealScalar>::dummy_precision(); }
 };
 
+template<> struct NumTraits<std::string>
+  : GenericNumTraits<std::string>
+{
+  enum {
+    RequireInitialization = 1,
+    ReadCost = HugeCost,
+    AddCost  = HugeCost,
+    MulCost  = HugeCost
+  };
+
+  static inline int digits10() { return 0; }
+
+private:
+  static inline std::string epsilon();
+  static inline std::string dummy_precision();
+  static inline std::string lowest();
+  static inline std::string highest();
+  static inline std::string infinity();
+  static inline std::string quiet_NaN();
+};
+
 } // end namespace Eigen
 
 #endif // EIGEN_NUMTRAITS_H

test/CMakeLists.txt

@@ -260,6 +260,7 @@ ei_add_test(ctorleak)
 ei_add_test(mpl2only)
 ei_add_test(inplace_decomposition)
 ei_add_test(half_float)
+ei_add_test(array_of_string)
 
 add_executable(bug1213 bug1213.cpp bug1213_main.cpp)
 

test/array_of_string.cpp

@@ -0,0 +1,32 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2016 Gael Guennebaud <gael.guennebaud@inria.fr>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include "main.h"
+
+void test_array_of_string()
+{
+  typedef Array<std::string,1,Dynamic> ArrayXs;
+  ArrayXs a1(3), a2(3), a3(3), a3ref(3);
+  a1 << "one", "two", "three";
+  a2 << "1", "2", "3";
+  a3ref << "one (1)", "two (2)", "three (3)";
+  std::stringstream s1;
+  s1 << a1;
+  VERIFY_IS_EQUAL(s1.str(), std::string("  one    two  three"));
+  a3 = a1 + std::string(" (") + a2 + std::string(")");
+  VERIFY((a3==a3ref).all());
+
+  a3 = a1;
+  a3 += std::string(" (") + a2 + std::string(")");
+  VERIFY((a3==a3ref).all());
+
+  a1.swap(a3);
+  VERIFY((a1==a3ref).all());
+  VERIFY((a3!=a3ref).all());
+}

unsupported/Eigen/CXX11/src/Tensor/TensorIO.h

@@ -13,11 +13,6 @@
 namespace Eigen {
 
 namespace internal {
-template<>
-struct significant_decimals_impl<std::string>
-    : significant_decimals_default_impl<std::string, true>
-{};
-
 
 // Print the tensor as a 2d matrix
 template <typename Tensor, int Rank>