评估大于string.size（）的负数 [英] negative number evaluating greater than string.size()
问题描述
下面是示例代码，演示了我遇到的问题。
将数字传递给函数时，我将其与字符串的大小进行比较，并且
然后采取某些行动，不幸的是在测试期间我发现负数被视为> 0.我
在mingw编译器/ dev c ++ / windows xp上编译了以下内容。
如果我将string.size（）替换为普通数字，它的行为正如所料？我
通知string.size（）返回大小类型而不是int但是我如何处理
那个？
预先感谢您的帮助
#include< iostream>
#include< stdlib.h>
#include < string>
使用命名空间std;
void something（int）;
int main（）
{
something（-1）;
system（PAUSE）;
返回0;
}
void something（int number）{
string str =" sdfjksdflksdjfkjsklfjsklfj" ;;
if（number< str.size（））{cout<< "你好" << ENDL; }
else {cout<< "伊克" << ENDL; }
}
Jason写道：下面是示例代码，演示我遇到的一个问题。
当一个数字传递给一个函数时，我将它与一个字符串的大小进行比较然后采取某些行动，不幸的是在测试期间我发现了负数被视为> 0.我在mingw编译器/ dev c ++ / windows xp上编译了以下内容。
如果我将string.size（）替换为普通数字，它的行为与预期一致？我注意string.size（）返回大小类型而不是int但是我该怎么处理呢
提前感谢您的帮助
GCC sez：
signed_probs.cpp：函数`void something（int）''：
signed_probs。 cpp：17：警告：签名和未签名之间的比较
整数表达式
将第17行更改为：
if（number< static_cast< int>（str.size（）））{cout<< "你好" << ENDL; }
解决了这个问题。
" Jason" < JA *********** @ btinternet.com>在消息中写道
news：c1 ********** @ titan.btinternet.com ...下面是示例代码，演示了我遇到的问题。
当一个数字传递给一个函数时，我将它与一个字符串的大小进行比较然后采取某些行动，不幸的是在测试期间我发现了这个消极数字被视为> 0.
我在mingw编译器/ dev c ++ / windows xp上编译了以下内容。
如果我将string.size（）替换为普通数字，它的行为与预期一致吗？
我注意到string.size（）返回大小类型而不是int但是如何处理
？
建议你阅读最近线程''时间摆脱未签名？''，于17/02/04开始
。
john
" Gianni Mariani" < GI ******* @ mariani.ws>在消息中写道
news：c1 ******** @ dispatch.concentric.net ...Jason写道：下面是示例代码，它演示了遇到
的问题。将数字传递给函数时，我将其与字符串的大小
进行比较然后采取某些操作，不幸的是在测试过程中我发现负数被视为> ; 0.
我在mingw编译器/ dev c ++ / windows xp上编译了以下内容。
如果我将string.size（）替换为普通数字，它的行为与预期一致吗？
我注意到string.size（）返回大小类型而不是int但是如何处理
呢？
提前感谢您提供任何帮助
GCC sez：
signed_probs.cpp：在函数`void something（int）''：
signed_probs.cpp：17：警告：有符号和无符号之间的比较
整数表达式
将第17行更改为：
if（number< static_cast< int>（str.size（）））{cout<< "你好" << ENDL; }
解决了这个问题。
当然这是OP应该做的，但请注意解决方案
有效地排除了字符串，其中size（）> INT_MAX。那么为什么要首先设计这样的
字符串呢？为什么没有size（）返回一个int？
john
Hi, below is example code which demonstrates a problem I have encountered.
When passing a number to a function I compare it with a string''s size and
then take certain actions, unfortunately during the testing of it I
discovered that negative numbers were being treated as if they were > 0. I
compiled the following on mingw compiler/dev c++/windows xp.
If I replace string.size() for a ordinary number it behaves as expected? I
notice string.size() returns size type and not an int but how do I deal with
that?
Thanks in advance for any help
#include <iostream>
#include <stdlib.h>
#include <string>
using namespace std;
void something(int);
int main()
{
something(-1);
system("PAUSE");
return 0;
}
void something(int number) {
string str = "sdfjksdflksdjfkjsklfjsklfj";
if(number < str.size()) { cout << " hello" << endl; }
else { cout << " eek" << endl; }
}
Jason wrote:Hi, below is example code which demonstrates a problem I have encountered.
When passing a number to a function I compare it with a string''s size and
then take certain actions, unfortunately during the testing of it I
discovered that negative numbers were being treated as if they were > 0. I
compiled the following on mingw compiler/dev c++/windows xp.
If I replace string.size() for a ordinary number it behaves as expected? I
notice string.size() returns size type and not an int but how do I deal with
that?
Thanks in advance for any help
GCC sez:
signed_probs.cpp: In function `void something(int)'':
signed_probs.cpp:17: warning: comparison between signed and unsigned
integer expressions
Changing line 17 to :
if(number < static_cast<int>(str.size())) { cout << " hello" << endl; }
solves the problem.
"Jason" <ja***********@btinternet.com> wrote in message
news:c1**********@titan.btinternet.com...Hi, below is example code which demonstrates a problem I have encountered.
When passing a number to a function I compare it with a string''s size and
then take certain actions, unfortunately during the testing of it I
discovered that negative numbers were being treated as if they were > 0. I compiled the following on mingw compiler/dev c++/windows xp.
If I replace string.size() for a ordinary number it behaves as expected? I notice string.size() returns size type and not an int but how do I deal with that?
Suggest you read the recent thread ''time to get rid of unsigned?'', started
on 17/02/04.
john
"Gianni Mariani" <gi*******@mariani.ws> wrote in message
news:c1********@dispatch.concentric.net...Jason wrote:Hi, below is example code which demonstrates a problem I have encountered. When passing a number to a function I compare it with a string''s size and then take certain actions, unfortunately during the testing of it I
discovered that negative numbers were being treated as if they were > 0. I compiled the following on mingw compiler/dev c++/windows xp.
If I replace string.size() for a ordinary number it behaves as expected? I notice string.size() returns size type and not an int but how do I deal with that?
Thanks in advance for any help
GCC sez:
signed_probs.cpp: In function `void something(int)'':
signed_probs.cpp:17: warning: comparison between signed and unsigned
integer expressions
Changing line 17 to :
if(number < static_cast<int>(str.size())) { cout << " hello" << endl; }
solves the problem.
Of course this is what the OP should do, but notice that the solution
effectively rules out strings where size() > INT_MAX. So why design for such
strings in the first place? Why not have size() return an int?
john
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