c++ - C++ 类型 unsigned long int

Question

unsigned long int 相当于unsigned long？_ 在 C++ 中

在我看来，它们是相同的。但我看到有些人仍在代码中使用 unsigned long int。不明白为什么？谁能为我解释一下

#include <stdio.h>

int main() {
    unsigned long int num = 282672; 
    int normalInt = 5;
    printf("");
    return 0;
}

Answer 1

是的。

long只是 的简写long int。这是因为原则long上只是一个限定符（例如，它也可以用于延长double数据类型）

来自 C++ ISO 标准，第 7.1.5.2 节，等效类型说明符表：

Answer 2

C99 标准的 §6.7.2 给出了以下类型列表（这只是摘录）：

• short, signed short, short int, 或signed short int
• unsigned short， 或者unsigned short int
• int, signed, 或signed int
• unsigned， 或者unsigned int
• long, signed long, long int, 或signed long int
• unsigned long， 或者unsigned long int
• long long, signed long long, long long int, 或signed long long int
• unsigned long long， 或者unsigned long long int

还有以下几点：

(5) 每个逗号分隔的集合指定相同的类型，除了对于位域，说明符int指定与 相同的类型signed int还是与 相同的类型是实现定义的unsigned int。

Answer 3

是的。unsigned, signed, short, long,long long都是XXX int.

请参阅标准中的7.1 说明符 [dcl.spec]：

3 [注意：由于signed、unsigned、long和short默认暗示int，出现在这些说明符之一之后的类型名称被视为（重新）声明的名称。[ 例子：

void h(unsigned Pc); // void h(unsigned int)

void k(unsigned int Pc); // void k(unsigned int)

—结束示例] —结束说明]

和7.1.6.2 简单类型说明符 [dcl.type.simple]

    Table 10 — simple-type-specifiers and the types they specify

    Specifier(s)            | Type
    ------------------------+---------------------------------
    type-name               | the type named
    simple-template-id      | the type as defined in 14.2
    char                    | “char”
    unsigned char           | “unsigned char”
    signed char             | “signed char”
    char16_t                | “char16_t”
    char32_t                | “char32_t”
    bool                    | “bool” 
    unsigned                | “unsigned int”
    unsigned int            | “unsigned int”
    signed                  | “int”
    signed int              | “int”
    int                     | “int”
    unsigned short int      | “unsigned short int”
    unsigned short          | “unsigned short int”
    unsigned long int       | “unsigned long int”
    unsigned long           | “unsigned long int”
    unsigned long long int  | “unsigned long long int”
    unsigned long long      | “unsigned long long int”
    signed long int         | “long int”

Answer 4

unsigned long int是正确的类型定义，但是int可以忽略。

Answer 5

是的，它们是一样的。说unsigned long int只是明确地说明它是一个 int。

您始终可以通过sizeof(unsigned long int)和查看类型的大小sizeof(unsigned long)

希望这可以帮助。