c++ - isdigit() 和 isnumber() 有什么区别？

Question

我的 ctype.h 中有函数 isnumber()。我在 http://www.cplusplus.com/reference/cctype/ 中都没有的书中找不到此函数的引用资料供咨询。我打算通过一个简单的例子来检测和显​​示 isdigit() 和 isnumber() 之间的区别，但是没有(此外，函数无法检测到 U+0C6A、U+0ED2 和 ½)。有什么不同吗？我该如何解决？

int main(int, char *[])
{
    string text("Hello½123, Poly౪ ໒girl0.5!!!");
    decltype(text.size()) punct = 0, alpha = 0, number = 0, space = 0, digit = 0, graf = 0;
    for(auto i : text) {
        if(ispunct(i)){
            cout << i << "<punct  ";
            ++punct;
        }
        if(isalpha(i)) {
            cout << i << "<alpha  ";
            ++alpha;
        }
        if(isnumber(i)) {
            cout << i << "<number  ";
            ++number;
        }
        if(isdigit(i)) {
            cout << i << "<digit  ";
            ++digit;
        }
        if(isgraph(i)) {
            cout << i << "<graph  ";
            ++graf;
        }
        if(isspace(i))
            ++space;
    }
    cout << endl << "There is " << endl;
    cout << punct <<  " puncts," << endl;
    cout << alpha << " alphas," << endl;
    cout << number << " numbers," << endl;
    cout << digit << " digits," << endl;
    cout << graf << " graphs," << endl;
    cout << space << " spaces" << endl;
    cout << "in " << text << endl;

    return 0;
}

部分结果:

...

5 numbers,
5 digits,
23 graphs,
2 spaces
in Hello½123, Poly౪ ໒girl0.5!!!

Answer 1

isnumber() 可能是特定于 Apple 的 C++ 方法(我手头没有 Mac 可以检查)。您可以在 Apple dev guide 中看到它:

The isnumber() function behaves similarly to isdigit(), but may recognize additional characters, depending on the current locale setting.

---

此外，isnumber() 在 Linux 上没有声明:我在 Linux 4.7.2 上使用 g++ 6.1.1 并得到错误:

g++ a.cpp
a.cpp: In function 'int main(int, char**)':
a.cpp:20:17: error: 'isnumber' was not declared in this scope
   if (isnumber(i)) {
                 ^

我也是用clang3.8.1测试的:

clang++ a.cpp --std=c++11
a.cpp:20:7: error: use of undeclared identifier 'isnumber'
                if (isnumber(i)) {
                    ^