added more flexible type-branching metaprogram for assign() promotion…

… in agrad matrix
stan-dev · Sep 11, 2012 · 2d5ac18 · 2d5ac18
1 parent 2842b0d
commit 2d5ac18
Show file tree

Hide file tree

Showing 2 changed files with 47 additions and 22 deletions.
diff --git a/src/stan/agrad/matrix.hpp b/src/stan/agrad/matrix.hpp
@@ -2367,33 +2367,39 @@ namespace stan {
           assign_to_var(x(m,n),y(m,n));
     }
 
-    inline void assign_to_nonvar(double& var, int val) {
-      var = val;
-    }
-    template <typename T1, typename T2>
-    inline void assign_to_nonvar(T1& var, const T2& val) {
-      throw std::domain_error("illegal assignment with mismatched LHS and RHS types");
-    }
-    template <typename T>
-    inline void assign_to_nonvar(T& var, const T& val) {
-      var = val;
-    }
-
 
     template <typename LHS, typename RHS>
-    inline void assign(LHS& var,
-                       const RHS& val) {
-      using stan::is_constant_struct;
-      if (is_constant_struct<RHS>::value 
-          && !is_constant_struct<LHS>::value)
-        assign_to_var(var,val);
-      else
-        assign_to_nonvar(var,val);
-    }
-
+    struct needs_promotion {
+      enum { value = ( is_constant_struct<RHS>::value 
+                       && !is_constant_struct<LHS>::value) };
+    };
 
+    template <bool PromoteRHS, typename LHS, typename RHS>
+    struct assigner {
+      static inline void assign(LHS& var, const RHS& val) {
+        throw std::domain_error("should not call base class of assigner");
+      }
+    };
+
+    template <typename LHS, typename RHS>
+    struct assigner<false,LHS,RHS> {
+      static inline void assign(LHS& var, const RHS& val) {
+        var = val;
+      }
+    };
+
+    template <typename LHS, typename RHS>
+    struct assigner<true,LHS,RHS> {
+      static inline void assign(LHS& var, const RHS& val) {
+        assign_to_var(var,val);
+      }
+    };
 
 
+    template <typename LHS, typename RHS>
+    inline void assign(LHS& var, const RHS& val) {
+      assigner<needs_promotion<LHS,RHS>::value, LHS, RHS>::assign(var,val);
+    }
 
 
 

diff --git a/src/test/agrad/matrix_test.cpp b/src/test/agrad/matrix_test.cpp
@@ -2958,6 +2958,7 @@ TEST(AgradMatrix, initializeVariable) {
 }
 
 TEST(AgradMatrix, assign) {
+  using stan::agrad::assign;
   using stan::agrad::var;
   using std::vector;
   using Eigen::Matrix;
@@ -2967,10 +2968,28 @@ TEST(AgradMatrix, assign) {
   assign(x,2.0);
   EXPECT_FLOAT_EQ(2.0,x.val());
 
+  assign(x,2);
+  EXPECT_FLOAT_EQ(2.0,x.val());
+
   var y(3.0);
   assign(x,y);
   EXPECT_FLOAT_EQ(3.0,x.val());
 
+  double xd;
+  assign(xd,2.0);
+  EXPECT_FLOAT_EQ(2.0,xd);
+
+  assign(xd,2);
+  EXPECT_FLOAT_EQ(2.0,xd);
+
+  int iii;
+  assign(iii,2);
+  EXPECT_EQ(2,iii);
+
+  unsigned int j = 12;
+  assign(iii,j);
+  EXPECT_EQ(12,j);
+
   vector<double> y_dbl(2);
   y_dbl[0] = 2.0;
   y_dbl[1] = 3.0;