Added a specific function for computing \vec{k}

src/fourier/details/euclidian_maps.hpp

@@ -113,6 +113,24 @@ namespace CosmoTool
 		   this->delta_k);
     }
 
+    template<typename Array, typename Array2>
+    void get_Kvec(const Array& ik, Array& kvec)
+    {
+      const DimArray& dims = this->getDims();
+      assert(ik.size() == dims.size());
+      assert(kvec.size() == dims.size());
+
+      kvec[0] = ik[0] * delta_k[0];
+      for (int q = 1; q < ik.size(); q++)
+	{
+	  int dk = ik[q];
+	  if (dk > dims[q]/2)
+	    dk = dk - dims[q];
+
+          kvec[q] = dk*delta_k[q];
+        }
+    }
+
     template<typename Array>
     double get_K(const Array& ik)
     {