Property function: is_symmetric_in.

docs/changelog.rst

@@ -13,6 +13,9 @@ v0.5 (not yet released)
 * Assignment operator for truth tables
   `#54 <https://github.com/msoeken/kitty/pull/54>`_
 
+* Function properties: ``is_symmetric_in``
+  `#55 <https://github.com/msoeken/kitty/pull/55>`_
+
 v0.4 (May 4, 2018)
 ------------------
 

docs/properties.rst

@@ -9,3 +9,4 @@ properties.
    is_canalizing
    is_horn
    is_krom
+   is_symmetric_in

include/kitty/properties.hpp

@@ -37,6 +37,8 @@
 #include <vector>
 
 #include "bit_operations.hpp"
+#include "operations.hpp"
+#include "operators.hpp"
 
 namespace kitty
 {
@@ -158,4 +160,18 @@ bool is_krom( const TT& tt )
   return true;
 }
 
+/*! \brief Checks whether a function is symmetric in a pair of variables
+
+  A function is symmetric in two variables, if it is invariant to swapping them.
+
+  \param tt Truth table
+  \param var_index1 Index of first variable
+  \param var_index2 Index of second variable
+*/
+template<typename TT>
+bool is_symmetric_in( const TT& tt, uint8_t var_index1, uint8_t var_index2 )
+{
+  return tt == swap( tt, var_index1, var_index2 );
+}
+
 } // namespace kitty