10.6.2 Write a class NormalPDF and compute its integral from −1.96 to 1.96.
解决这个问题，尝试实现了一个NormalPDF类并进行了简单的测试，代码并不保证完全正确，仅供参考。
NormalPDF.h
#pragma once
#include "RealFunction.h"
#include "matlib.h"
#include "testing.h"
class NormalPDF : public RealFunction {
public:
NormalPDF();
double v;
double evaluate(double x);
double integral(double a, double b, int nPoints);
};
void testNormalPDFIntergal();NormalPDF.cpp
#include "NormalPDF.h"
#include <cmath>
NormalPDF::NormalPDF() {
v = 0;
}
double NormalPDF::evaluate(double x) {
static const double inv_sqrt_2pi = 0.3989422804014327;
return inv_sqrt_2pi * std::exp(-0.5 * x * x);
}
double NormalPDF::integral(double a, double b, int nPoints) {
double h = (b - a) / nPoints;
double x = a + 0.5 * h;
double total = 0.0;
for (int i = 0; i < nPoints; i++) {
double y = evaluate(x);
total += y;
x += h;
}
return h * total;
}
/*
TESTS for NormalPDF
*/
static void testNormalPDF() {
rng("default");
NormalPDF nPdf;
double p = nPdf.integral(-1.96, 1.96,10000);
ASSERT_APPROX_EQUAL(p, 0.95, 0.1);
}
static void testEvaluate0() {
rng("default");
NormalPDF nPdf;
double p = nPdf.evaluate(-1000000000);
ASSERT_APPROX_EQUAL(p, 0, 0.1);
}
static void testEvaluate1() {
rng("default");
NormalPDF nPdf;
double p1 = nPdf.evaluate(0);
ASSERT_APPROX_EQUAL(p1, 0.3989, 0.1);
}
static void testEvaluate2() {
rng("default");
NormalPDF nPdf;
double p2 = nPdf.evaluate(10000000000);
ASSERT_APPROX_EQUAL(p2, 0, 0.1);
}
void testNormalPDFIntergal() {
TEST(testNormalPDF);
TEST(testEvaluate0);
TEST(testEvaluate1);
TEST(testEvaluate2);
}
京公网安备 11010702002337 号