remove is_zero function from matrix interface

The `is_zero` shouldn't be part of the matrix type requirements,
instead it should be a part of the scalar type requirements.

Test: build
Issue: saebyn#26
Signed-off-by: Gluttton <gluttton@ukr.net>

Author: Gluttton

README.md

@@ -173,10 +173,10 @@ The `munkres.h` header file contains the solver sources. The solver takes input
 The current implementation doesn't depend on a specific matrix type and can be used with an arbitrary data type that meets the following requirements:
  - the container type must implement the subscription operator `operator ()` that takes two parameters (row and column) and return a corresponding element of a matrix;
  - the container type must implement the `columns` and `rows` member functions that return matrix dimension;
- - the container type must implement the `is_zero` member function that allows testing a selected element is it zero;
  - the container type must implement the `begin` and `end` member functions that return appropriate iterators.
 
 Also, the library doesn't require any specific type for a scalar element of the matrix, so any arbitrary data type can be used that meets the following requirements:
+ - the element type must comparable with zero;
  - the element type must implement comparison operators (`<`, `>`);
  - the element type must implement addition and subtraction (`+`, `-`);
  - the element type must implement the assignment operator (`=`).

src/munkres-cpp/matrix_base.h

@@ -19,7 +19,6 @@
 #if !defined(__MUNKRES_CPP_MATRIX_BASE_H__)
 #define __MUNKRES_CPP_MATRIX_BASE_H__
 
-#include <cmath>
 #include <iterator>
 
 
@@ -43,15 +42,6 @@ struct matrix_base
     // Default implementation.
     virtual ~matrix_base () = default;
 
-    // Implementation.
-    template <typename V = value_type>
-    constexpr typename std::enable_if<std::is_integral<V>::value, bool>::type
-    is_zero (size_t row, size_t column) const {return operator () (row, column) == 0;}
-
-    template <typename V = value_type>
-    constexpr typename std::enable_if<!std::is_integral<V>::value, bool>::type
-    is_zero (size_t row, size_t column) const {return FP_ZERO == std::fpclassify (operator () (row, column) );}
-
     // Allow to use standard algorithms.
     template <typename M>
     struct iterator : public std::iterator<std::input_iterator_tag, typename M::value_type>

src/munkres-cpp/munkres.h

@@ -21,6 +21,7 @@
 #define _MUNKRES_H_
 
 #include <algorithm>
+#include <cmath>
 #include <forward_list>
 #include <limits>
 
@@ -29,6 +30,16 @@
 namespace munkres_cpp
 {
 
+template <typename T>
+static constexpr typename std::enable_if<std::is_integral<T>::value, bool>::type
+is_zero (const T & v) {return v == 0;}
+
+template <typename T>
+static constexpr typename std::enable_if<!std::is_integral<T>::value, bool>::type
+is_zero (const T & v) {return FP_ZERO == std::fpclassify (v);}
+
+
+
 template<typename T, template <typename> class M>
 class Munkres
 {
@@ -93,7 +104,7 @@ bool Munkres<T, M>::find_uncovered_in_matrix (size_t & row, size_t & col) const
         if (!col_mask[col])
             for (row = 0; row < size; row++)
                 if (!row_mask[row])
-                    if (matrix.is_zero (row, col) )
+                    if (is_zero (matrix (row, col) ) )
                         return true;
 
     return false;
@@ -106,7 +117,7 @@ int Munkres<T, M>::step1 ()
 {
     for (size_t row = 0; row < size; row++) {
         for (size_t col = 0; col < size; col++) {
-            if (matrix.is_zero (row, col) ) {
+            if (is_zero (matrix (row, col) ) ) {
                 for (size_t nrow = 0; nrow < row; nrow++)
                     if (STAR == mask_matrix (nrow, col) )
                         goto next_column;
@@ -226,7 +237,7 @@ int Munkres<T, M>::step5 ()
         if (!col_mask[col])
             for (size_t row = 0; row < size; row++)
                 if (!row_mask[row])
-                    if (h > matrix (row, col) && !matrix.is_zero (row, col) )
+                    if (h > matrix (row, col) && !is_zero (matrix (row, col) ) )
                         h = matrix (row, col);
 
     for (size_t row = 0; row < size; row++)