我收到错误消息:
error: comparison of constant 18446744073709551614 with expression of type 'unsigned int' is always true [-Werror,-Wtautological-constant-out-of-range-compare]
The line of code it is referring to is this:
if (key_index != std::string::npos)
key_index
是我的unsigned int
语句也位于的main()
函数中的if
局部变量。我已经在这里阅读了几篇文章,试图弄清我要去哪里。
此链接是最有用的
What does string::npos mean
但是,即使利用那里的建议,我仍然会遇到相同的错误。
我尝试创建自己的变量:
const int NPOS = -1
我以几种不同的方式修改了比较运算符。
我试图将这条线变成:
if(key_index != (std::string::npos -1))
我已经尝试了其他一些小的更改,目前还无法记忆。
我忘了写下来,对于没有全部测试/ retrofit 细节,我深表歉意。
这是问题来自的完整
main()
代码。就我所知,可能还需要其他一些纠正。#include <SFML/Graphics.hpp>
#include <SFML/System.hpp>
#include <SFML/Audio.hpp>
#include <SFML/Window.hpp>
#include <math.h> // For pow()
#include <string>
#include <stdexcept> // For std::runtime_error
#include <vector>
#include "GuitarString.hpp"
const sf::Uint32 quit_key = 27; // ASCII 27 is the Escape key
const std::string keyboard = "q2we4r5ty7u8i9op-[=zxdcfvgbnjmk,.;/' ";
const int num_keys = keyboard.length();
const int kDuration = 8;
std::vector<sf::Int16> makeSamplesFromString(GuitarString *gs) {
std::vector<sf::Int16> samples;
gs->pluck();
for (int i= 0; i < kSampleRate * kDuration; i++) {
gs->tic();
samples.push_back(gs->sample());
}
return samples;
}
int main() {
sf::Event event;
double frequency;
unsigned int key_index;
std::vector < std::vector<sf::Int16> > samples(num_keys);
std::vector<sf::SoundBuffer> buffers(num_keys);
std::vector<sf::Sound> sounds(num_keys);
for (int i = 0; i < num_keys; ++i) {
frequency = 440 * pow(2, (i-24) / 12.0L);
GuitarString gs = GuitarString(frequency);
samples[i] = makeSamplesFromString(&gs);
if (!buffers[i].loadFromSamples(&samples[i][0],
samples[i].size(), 2, kSampleRate)) {
throw std::runtime_error("sf::SoundBuffer: failed to load from samples.");
}
sounds[i].setBuffer(buffers[i]);
}
sf::Vector2u size_win(500, 200);
sf::Sprite background_sprite;
sf::Texture background_texture;
if (background_texture.loadFromFile("keyboard.png")) {
background_sprite.setTexture(background_texture);
size_win = background_texture.getSize();
}
sf::RenderWindow window(sf::VideoMode(size_win.x, size_win.y),
" PS5B GuitarHero - Press Escape to Exit ");
window.setKeyRepeatEnabled(false);
while (window.isOpen()) {
while (window.pollEvent(event)) {
switch (event.type) {
case sf::Event::Closed:
window.close();
break;
case sf::Event::TextEntered:
key_index = keyboard.find(event.text.unicode);
if (key_index != std::string::npos) { // the line causing the issue….
sounds[key_index].play();
} else if (event.text.unicode == quit_key) {
window.close();
}
break;
default:
break;
}
window.clear(sf::Color::Black);
window.draw(background_sprite);
window.display();
}
}
return 0;
}
最佳答案
如果您使用的是64位系统,则std::string::npos
几乎可以肯定是64位数字。为了确保最大的可移植性,请使用std::string
指定的类型。
std::string::size_type key_index;
不管您使用的是32位还是64位系统,这都应该有效。
关于c++ - unsigned int的比较始终为真(npos问题?),我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/49566816/