Adding the first moment of a histogram panel

cmake/unit_testing.cmake

@@ -39,6 +39,7 @@ add_subdirectory( src/scion/integration/LinearLinear/test )
 add_subdirectory( src/scion/integration/LinearLogarithmic/test )
 add_subdirectory( src/scion/integration/LogarithmicLinear/test )
 add_subdirectory( src/scion/integration/LogarithmicLogarithmic/test )
+add_subdirectory( src/scion/integration/FirstMomentHistogram/test )
 add_subdirectory( src/scion/integration/FirstMomentLinearLinear/test )
 add_subdirectory( src/scion/integration/GaussLegendre/2/test )
 add_subdirectory( src/scion/integration/GaussLegendre/4/test )

src/scion/integration/FirstMomentHistogram.hpp

@@ -0,0 +1,54 @@
+#ifndef NJOY_SCION_INTEGRATION_FIRSTMOMENTHISTOGRAM
+#define NJOY_SCION_INTEGRATION_FIRSTMOMENTHISTOGRAM
+
+// system includes
+
+// other includes
+#include "scion/integration/IntegratorBase.hpp"
+
+namespace njoy {
+namespace scion {
+namespace integration {
+
+  /**
+   *  @class
+   *  @brief First raw moment of a histogram panel (y is constant in x)
+   *
+   *  The first raw moment or mean is defined as the integral of x * f(x)
+   */
+  class FirstMomentHistogram : public IntegratorBase< FirstMomentHistogram > {
+
+    /* friend declarations */
+    friend class IntegratorBase< FirstMomentHistogram >;
+
+    /* interface implementation functions */
+
+    /**
+     *  @brief Perform first raw moment integration of a histogram panel (y is constant in x)
+     *
+     *  @param[in] xLeft    the left value on the x interval
+     *  @param[in] xRight   the right value on the x interval
+     *  @param[in] yLeft    the left value on the y interval
+     *  @param[in] yRight   the right value on the y interval
+     */
+    template < typename X, typename Y,
+               typename I = decltype( std::declval< X >() * std::declval< X >() * std::declval< Y >() ) >
+    I integrate( const X& xLeft, const X& xRight,
+                 const Y& yLeft, const Y& ) const noexcept {
+
+      return 0.5 * yLeft * ( xRight - xLeft ) * ( xRight + xLeft );
+    }
+
+  public:
+
+    using IntegratorBase::operator();
+  };
+
+  // integration function
+  static constexpr FirstMomentHistogram firstMomentHistogram;
+
+} // integration namespace
+} // scion namespace
+} // njoy namespace
+
+#endif

src/scion/integration/FirstMomentHistogram/test/CMakeLists.txt

@@ -0,0 +1 @@
+add_cpp_test( integration.FirstMomentHistogram FirstMomentHistogram.test.cpp )

src/scion/integration/FirstMomentHistogram/test/FirstMomentHistogram.test.cpp

@@ -0,0 +1,57 @@
+// include Catch2
+#include <catch2/catch_test_macros.hpp>
+#include <catch2/matchers/catch_matchers_floating_point.hpp>
+using Catch::Matchers::WithinRel;
+
+// what we are testing
+#include "scion/integration/FirstMomentHistogram.hpp"
+
+// other includes
+
+// convenience typedefs
+using namespace njoy::scion;
+
+SCENARIO( "FirstMomentHistogram" ) {
+
+  GIVEN( "FirstMomentHistogram integration object" ) {
+
+    WHEN( "integrating an interval" ) {
+
+      integration::FirstMomentHistogram integrator{};
+
+      THEN( "the integration is performed correctly" ) {
+
+        double xLeft = 1.0;
+        double xRight = 2.0;
+        double yLeft = 1.0;
+        double yRight = 4.0;
+
+        // both y values are the same
+        CHECK_THAT( 1.5, WithinRel( integrator( xLeft, xRight, yLeft, yLeft ) ) );
+
+        // the y values are different
+        CHECK_THAT( 1.5, WithinRel( integrator( xLeft, xRight, yLeft, yRight ) ) );
+      } // THEN
+    } // WHEN
+  } // GIVEN
+
+  GIVEN( "linlin integration function" ) {
+
+    WHEN( "integrating an interval" ) {
+
+      THEN( "the integration is performed correctly" ) {
+
+        double xLeft = 1.0;
+        double xRight = 2.0;
+        double yLeft = 1.0;
+        double yRight = 4.0;
+
+        // both y values are the same
+        CHECK_THAT( 1.5, WithinRel( integration::firstMomentHistogram( xLeft, xRight, yLeft, yLeft ) ) );
+
+        // the y values are different
+        CHECK_THAT( 1.5, WithinRel( integration::firstMomentHistogram( xLeft, xRight, yLeft, yRight ) ) );
+      } // THEN
+    } // WHEN
+  } // GIVEN
+} // SCENARIO

src/scion/integration/FirstMomentLinearLinear.hpp

@@ -12,7 +12,7 @@ namespace integration {
 
   /**
    *  @class
-   *  @brief First raw moment of a Linear-linear panel (y is linear in x)
+   *  @brief First raw moment of a linear-linear panel (y is linear in x)
    *
    *  The first raw moment or mean is defined as the integral of x * f(x)
    */