- Added the tmax, tmin, and tabs templates

- Changed the diag() function so that it is allowed to take
     non-square matrices.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402697

dlib/algs.h

@@ -568,6 +568,52 @@ namespace dlib
     inline double put_in_range(const double& a, const double& b, const double& val)
     { return put_in_range<double>(a,b,val); }
 
+// ----------------------------------------------------------------------------------------
+
+    /*! tabs 
+
+        This is a template to compute the absolute value a number at compile time.
+
+        For example,
+            abs<-4>::value == 4
+            abs<4>::value == 4
+    !*/
+
+        template <long x, typename enabled=void>
+        struct tabs { const static long value = x; };
+        template <long x>
+        struct tabs<x,typename enable_if_c<(x < 0)>::type> { const static long value = -x; };
+
+// ----------------------------------------------------------------------------------------
+
+    /*! tmax
+
+        This is a template to compute the max of two values at compile time
+
+        For example,
+            abs<4,7>::value == 7
+    !*/
+
+        template <long x, long y, typename enabled=void>
+        struct tmax { const static long value = x; };
+        template <long x, long y>
+        struct tmax<x,y,typename enable_if_c<(y > x)>::type> { const static long value = y; };
+
+// ----------------------------------------------------------------------------------------
+
+    /*! tmin 
+
+        This is a template to compute the min of two values at compile time
+
+        For example,
+            abs<4,7>::value == 4
+    !*/
+
+        template <long x, long y, typename enabled=void>
+        struct tmin { const static long value = x; };
+        template <long x, long y>
+        struct tmin<x,y,typename enable_if_c<(y < x)>::type> { const static long value = y; };
+
 // ----------------------------------------------------------------------------------------
 
     /*!A is_function 

dlib/matrix/matrix_utilities.h

@@ -2948,7 +2948,7 @@ convergence:
         template <typename EXP>
         struct op : has_destructive_aliasing
         {
-            const static long NR = EXP::NC;
+            const static long NR = (EXP::NC&&EXP::NR)? (tmin<EXP::NR,EXP::NC>::value) : (0);
             const static long NC = 1;
             typedef typename EXP::type type;
             typedef typename EXP::mem_manager_type mem_manager_type;
@@ -2957,7 +2957,7 @@ convergence:
             { return m(r,r); }
 
             template <typename M>
-            static long nr (const M& m) { return m.nr(); }
+            static long nr (const M& m) { return std::min(m.nc(),m.nr()); }
             template <typename M>
             static long nc (const M& m) { return 1; }
         };
@@ -2970,14 +2970,6 @@ convergence:
         const matrix_exp<EXP>& m
     )
     {
-        // You can only get the diagonal for square matrices.
-        COMPILE_TIME_ASSERT(EXP::NR == EXP::NC);
-        DLIB_ASSERT(m.nr() == m.nc(), 
-            "\tconst matrix_exp diag(const matrix_exp& m)"
-            << "\n\tYou can only apply diag() to a square matrix"
-            << "\n\tm.nr(): " << m.nr()
-            << "\n\tm.nc(): " << m.nc() 
-            );
         typedef matrix_unary_exp<matrix_exp<EXP>,op_diag> exp;
         return matrix_exp<exp>(exp(m));
     }

dlib/quantum_computing/quantum_computing.h

@@ -8,6 +8,7 @@
 #include "../matrix.h"
 #include "../rand.h"
 #include "../enable_if.h"
+#include "../algs.h"
 #include "quantum_computing_abstract.h"
 
 namespace dlib
@@ -34,22 +35,6 @@ namespace dlib
 
     // ------------------------------------------------------------------------------------
 
-    // This is a template to compute the absolute value a number at compile time
-        template <long x, typename enabled=void>
-        struct abs { const static long value = x; };
-        template <long x>
-        struct abs<x,typename enable_if_c<(x < 0)>::type> { const static long value = -x; };
-
-    // ------------------------------------------------------------------------------------
-
-    // This is a template to compute the max of two values at compile time
-        template <long x, long y, typename enabled=void>
-        struct max { const static long value = x; };
-        template <long x, long y>
-        struct max<x,y,typename enable_if_c<(y > x)>::type> { const static long value = y; };
-
-    // ------------------------------------------------------------------------------------
-
     }
 
     typedef std::complex<double> qc_scalar_type;
@@ -657,7 +642,7 @@ namespace dlib
                     target_mask <<= 1;
             }
 
-            static const long num_bits = qc_helpers::abs<control_bit-target_bit>::value+1;
+            static const long num_bits = tabs<control_bit-target_bit>::value+1;
             static const long dims = qc_helpers::exp_2_n<num_bits>::value;
 
             const qc_scalar_type operator() (long r, long c) const 
@@ -742,8 +727,8 @@ namespace dlib
                     target_mask <<= 1;
             }
 
-            static const long num_bits = qc_helpers::max<qc_helpers::abs<control_bit1-target_bit>::value, 
-                                                         qc_helpers::abs<control_bit2-target_bit>::value>::value+1;
+            static const long num_bits = tmax<tabs<control_bit1-target_bit>::value, 
+                                              tabs<control_bit2-target_bit>::value>::value+1;
             static const long dims = qc_helpers::exp_2_n<num_bits>::value;
 
             const qc_scalar_type operator() (long r, long c) const 

dlib/test/matrix.cpp

@@ -120,6 +120,10 @@ namespace
         mrc.set_size(3,4);
 
         set_all_elements(mrc,1);
+
+        DLIB_CASSERT(diag(mrc) == uniform_matrix<double>(3,1,1),"");
+        DLIB_CASSERT(diag(matrix<double>(mrc)) == uniform_matrix<double>(3,1,1),"");
+
         matrix<double,2,3> mrc2;
         set_all_elements(mrc2,1);
         DLIB_CASSERT((removerc<1,1>(mrc) == mrc2),"");