逗号左边的操作数没有效果? [英] left-hand operand of comma has no effect?
本文介绍了逗号左边的操作数没有效果?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我在这个警告消息中遇到了一些麻烦,它在一个模板容器类中实现
int k = 0 ,l = 0; (k =(index + 1),l = 0; k elements [k] = arryCpy [1] ;
}
delete [] arryCpy;
这是我得到的警告
cont.h:在成员函数`void Container< T> :: insert(T,int)'中:
cont.h:99:警告:逗号的左侧操作数没有任何作用
cont.h:在成员函数`void Container< T> :: insert(T,int)[with T = double]':
a5testing.cpp:21:从这里实例化
cont.h:99:warning:逗号左操作数没有效果
cont.h:在成员函数`void Container< T> :: insert(T,int)[with T = std :: string]':
a5testing.cpp:28:从这里实例化
cont.h:99:警告:逗号的左侧操作数不起作用
>退出代码:0
解决方案 逗号表达式
a, b,c,d,e
类似于 {
a;
b;
c;
d;
return e;
}
因此, k
l < (sizeC - index)
。
要合并条件,请使用&&
或 ||
。
k < sizeC&& l< (sizeC-index)//两者都必须满足
k< sizeC || l< (sizeC-index)//任何一个都可以。
I'm having some trouble with this warning message, it is implemented within a template container class
int k = 0, l = 0;
for ( k =(index+1), l=0; k < sizeC, l < (sizeC-index); k++,l++){
elements[k] = arryCpy[l];
}
delete[] arryCpy;
this is the warning i get
cont.h: In member function `void Container<T>::insert(T, int)':
cont.h:99: warning: left-hand operand of comma has no effect
cont.h: In member function `void Container<T>::insert(T, int) [with T = double]':
a5testing.cpp:21: instantiated from here
cont.h:99: warning: left-hand operand of comma has no effect
cont.h: In member function `void Container<T>::insert(T, int) [with T = std::string]':
a5testing.cpp:28: instantiated from here
cont.h:99: warning: left-hand operand of comma has no effect
>Exit code: 0
解决方案
The comma expression a,b,c,d,e
is similar to
{
a;
b;
c;
d;
return e;
}
therefore, k<sizeC, l<(sizeC - index)
will only return l < (sizeC - index)
.
To combine conditionals, use &&
or ||
.
k < sizeC && l < (sizeC-index) // both must satisfy
k < sizeC || l < (sizeC-index) // either one is fine.
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