left-hand operand of comma has no effect?
I'm having some trouble with this warning message, it is implemented within a template container class
开发者_如何学运维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
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.
The expression k < sizeC, l < (sizeC-index)
only returns the result of the right-hand test. Use &&
to combine tests:
k < sizeC && l < (sizeC-index)
Change to:
for ( k =(index+1), l=0; k < sizeC && l < (sizeC-index); k++,l++){
When you have a comma expression is evaluated the rightmost argument is returned so your:
k < sizeC, l < (sizeC-index)
expression evaluates to:
l < (sizeC-index)
and thus misses
k < sizeC
use the &&
to combine the conditions instead.
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