blocks|key|2308697|text|if+(x==1)没有错误。当您将布尔值转换为数值类型时，所有真值表示形式都将转换为1。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2308698|给定bool+z=true，if(z>0.5)将为真，因为1.0大于0.5。|2308699|entityMap^0|0|9|0|2|B|E|9|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|R|8|@]|D|@]|E|$]]]|I|$]]

<code>if (x==1)</code> is not incorrect. All true value representations are converted to 1 when you convert a boolean to a numeric type.

Given <code>bool z=true</code>, <code>if(z&gt;0.5)</code> will be true, because 1.0 is greater than 0.5.

blocks|key|2520472|text|bool只有两个值，分别是true和false。1和0是整型文字，因此可以将它们转换为bool。您必须考虑到转换在两个方向上都有效，但您不一定会得到相同的整数：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2520473|int+a+=+5;
bool+b+=+a;+//+int+->+bool+conversion
int+c+=+b;++//+bool+->+int+conversion
std::cout+<<+a+<<+"+"+c;|code-block|syntax|javascript|2520474|打印：|2520475|5+1|2520476|0以外的任何整数值都会转换为true，但true始终会转换为1。|2520477|记住这一点，您的所有示例都将按预期工作。但是，请注意，bool的主要用途是我们可以在代码中使用true和false，而不必将数字作为0和1的特殊含义。显式总是更好，所以当你说true时，你最好写true而不是1。|2520478|entityMap^0|0|4|D|4|I|5|O|1|Q|1|17|4|0|0|0|0|0|1|E|4|K|4|U|1|0|R|4|1B|4|1G|5|1U|1|1W|1|2F|4|2P|4|2W|1|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|17|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|18|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1A|8|@$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]|$9|1H|A|1I|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1J|8|@$9|1K|A|1L|B|C]|$9|1M|A|1N|B|C]|$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]|$9|1S|A|1T|B|C]|$9|1U|A|1V|B|C]|$9|1W|A|1X|B|C]|$9|1Y|A|1Z|B|C]]|D|@]|E|$]]|$1|S|3|-4|5|6|7|20|8|@]|D|@]|E|$]]]|T|$]]

<code>bool</code> has only two values, and they are <code>true</code> and <code>false</code>. <code>1</code> and <code>0</code> are integer literals and as such they can be converted to <code>bool</code>. You have to consider that the conversion works in both directions, but you do not necessarily get back the same integer:

<pre><code>int a = 5;
bool b = a; // int -&gt; bool conversion
int c = b; // bool -&gt; int conversion
std::cout &lt;&lt; a &lt;&lt; " " c;
</code></pre>

prints:

<pre><code>5 1
</code></pre>

Any integer value other than <code>0</code> gets converted to <code>true</code>, but <code>true</code> gets always converted to <code>1</code>.

Keeping this in mind, all your examples will work as expected. However, note that <code>bool</code>s main purpose is that we can use <code>true</code> and <code>false</code> in our code instead of having to give numbers as <code>0</code> and <code>1</code> special meaning. It is always better to be explicit, so when you mean <code>true</code> you better write <code>true</code> not <code>1</code>.

blocks|key|2520631|text|这里的一个相关问题是“为什么我们甚至允许在bool和int之间进行比较？”|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2520632|答案是向后兼容和折衷，因为C和C%2B%2B过去推荐使用整数来存储布尔值。所以有很多代码|2520633|尽管有新的语言规则，|2520634|仍应继续工作，例如关系运算符返回布尔值而不是整型值。|ordered-list-item|2520635|允许您通过更改布尔变量的声明来升级旧代码，而只需对其余代码进行最少的后续更改。|2520636|2520637|在这方面，其他语言可能更干净，但是bool类型显然是成功的。|2520638|entityMap^0|L|4|Q|3|0|0|0|0|0|0|H|4|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|Z|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|10|8|@]|D|@]|E|$]]|$1|M|3|N|5|L|7|11|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|12|8|@]|D|@]|E|$]]|$1|P|3|Q|5|6|7|13|8|@$9|14|A|15|B|C]]|D|@]|E|$]]|$1|R|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|S|$]]

A relevant question here is &quot;why do we even allow comparison between a <code>bool</code> and an <code>int</code>?&quot;.
The answer is backward compatibility and compromise, because C and C++ used to recommend integers to store Boolean values. So there was a lot of code that
<ol>
<li>Should keep working in spite of new language rules, such that
relational operators return a bool instead of an int.</li>
<li>Allow you to upgrade old code by changing the declaration of a Boolean variable
with a minimum of follow-up changes in the rest of the code.</li>
</ol>
Other languages may be cleaner in this respect, but the <code>bool</code> type has apparantly been a success.

The <code>bool</code> data type is commonly represented as <code>0</code> (as <code>false</code>) and <code>1</code> (as <code>true</code>). However, some say that <code>true</code> values can be represented by a value other than <code>1</code>. If the later statement is <code>true</code>, then the following expression may be incorrect.

<pre><code>bool x = 1;
if (x==1)
 Do something..
</code></pre>

I am wondering if the following statements would work as desired and expected on commonly used compilers.

<ol>
<li>&nbsp;

<pre><code>bool x = 1;
if (x==1)
 Do something.
</code></pre></li>
<li>&nbsp;

<pre><code>bool y = 0;
if (y&gt;0.5)
 Do something..
</code></pre></li>
<li>&nbsp;

<pre><code>bool z = 1;
if(z&gt;0.5)
 Do something...
</code></pre></li>
</ol>

Comparison of bool data types in C++

编译器

bool数据类型通常表示为0 (如false)和1 (如true)。但是，有些人说true值可以用1以外的值来表示。如果后面的语句为true，则以下表达式可能不正确。bool x = 1;if (x==1)    Do something..我想知道下面的语句在常用的编译器上是否能像预期的那样工作。if () Do s...

问C++中布尔数据类型的比较
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