比较字符串和“”字符串字面量 [英] compare string and "" string literal

问题描述

将字符串对象与"进行比较是否正确和安全，引用空字符串的一对

引号？如果字符串对象：s ="" ;;

s包含一个''\''？使用std :: string :: size或

std :: string :: empty来处理这种情况会更好吗？谢谢。


string s ="" ;;

if（s ==""）;

if（s.size == 0）;

if（s.empty（））;

解决方案

< blockquote>


On 1 ??24è？，é???10ê±41·?,lovecreatesbea ... @ gmail.com

< lovecreatesbea ... @ gmail.comwrote：

将字符串对象与"，一对
进行比较是否正确和安全
引号引用空字符串？如果字符串对象：s ="" ;;

s包含一个''\''？使用std :: string :: size或

std :: string :: empty来处理这种情况会更好吗？谢谢。


string s ="" ;;

if（s ==""）;

if（s.size == 0）;

if（s.empty（））;

（对不起前一篇文章中的错误）


比较字符串对象和是否正确和安全 ;，一对

引号引用空字符串？如果字符串对象：s ="" ;;

包含一个''\ 0''？使用std :: string :: size或

std :: string :: empty来处理这种情况会更好吗？


string s =" ;" ;;

if（s ==""）;

if（s.size == 0）;

if （s.empty（））;

lovecreatesbea ... @ gmail.coma¨|暴击：

>


比较字符串对象与"，引用一对

引号是否正确和安全空字符串？

是的，编译器创建一个用"初始化的临时字符串。

执行比较。

如果字符串对象：s ="" ;;

包含一个''\ 0''？

这是实现depedant，唯一的要求是

c_str（）方法返回一个0终止的POD char *。 br />

使用std :: string :: size或

std :: string :: empty更好地处理这种情况？

除非你有特别的理由不这样做，否则

std :: string :: empty更清晰。

>

string s ="" ;;

if（s ==""）;

花费中间对象和调用比较函数，除非

有某种优化（？）。

if（s.size == 0）;

值得注意的是std :: string :: size复杂度在

容器的大小中可能是线性的;但它应该适用于主字符串实现。

if（s.empty（））;

它可能相当于a.size（）== 0但预计会在

摊销的常数时间内运行;如果确实有效，可能会更快。

Michael

2007年1月24日星期三08:53:19 +0100，Michael DOUBEZ写道：

> lovecreatesbea ... @ gmail.coma¨|暴击：

>比较一个字符串对象与"，引用空字符串的一对引号是否正确和安全？

是的，编译器会创建一个用"初始化的临时字符串。
进行比较。

编译器不会创建临时字符串。一些实现

在内部创建一个临时字符串，但这是一个不同的问题。


祝福，

Roland Pibinger

Is it correct and safe to compare a string object with "", a pair of
quotation marks quoted empty string?If the string object: s = ""; does
s contain a single ''\''? Is it better to use std::string::size or
std::string::empty to deal with this condition? Thank you.

string s = "";
if (s == "");
if (s.size == 0);
if (s.empty());

解决方案

On 1??24è?, é???10ê±41·?, "[e-mail]"
<[e-mail]:

Is it correct and safe to compare a string object with "", a pair of
quotation marks quoted empty string?If the string object: s = ""; does
s contain a single ''\''? Is it better to use std::string::size or
std::string::empty to deal with this condition? Thank you.

string s = "";
if (s == "");
if (s.size == 0);
if (s.empty());

(sorry for the mistakes in my previous post)

Is it correct and safe to compare a string object with "", a pair of
quotation marks quoted empty string? If the string object: s = ""; does
s contain a single ''\0''? Is it better to use std::string::size or
std::string::empty to deal with this condition?

string s = "";
if (s == "");
if (s.size == 0);
if (s.empty());

[e-mail] a ¨|crit :

>

Is it correct and safe to compare a string object with "", a pair of
quotation marks quoted empty string?

Yes, the compiler creates a temporary string initialized with "" to
perform the comparison.

If the string object: s = ""; does
s contain a single ''\0''?

This is implementation depedant, the only requirement is that the
c_str() method returns a POD char* which is 0 terminated.

Is it better to use std::string::size or
std::string::empty to deal with this condition?

Unless you have a specific reason to do otherwise, the
std::string::empty is the clearer.

>
string s = "";
if (s == "");

Costs a intermediary object and a call to a comparison function unless
there is some kind of optimisation (?).

if (s.size == 0);

It is to note that std::string::size complexity may be linear in the
container''s size; but it should work fine with main string implementations.

if (s.empty());

It may be equivalent to a.size() == 0 but it is expected to run in
amortized constant time; it may be faster if that does count.
Michael

On Wed, 24 Jan 2007 08:53:19 +0100, Michael DOUBEZ wrote:

>[e-mail] a ¨|crit :

>Is it correct and safe to compare a string object with "", a pair of
quotation marks quoted empty string?

Yes, the compiler creates a temporary string initialized with "" to
perform the comparison.

The compiler does not create a temporary string. Some implementations
internally create a temporary string but that is a different question.

Best wishes,
Roland Pibinger

这篇关于比较字符串和“”字符串字面量的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！