Re: Question about namespace
Bill Oliver wrote:
I have written a little image processing class and one of the things
I do is calculate the power of an image defined as the sum of the
absolute values of all the pixels. Here's the snippet, where
nchannels (e.g. number of colors) and npoints (i.e. number of pixels
in the image) are a public variables:
file: utils.cpp
using namespace std;
template<class T>
vector<T>
image<T>::power(){
vector<T> result(nchannels);
vector<T> val(nchannels);
for(int k=0;k<nchannels;k++) val[k] = (T)0.0;
for(int i=0;i<npoints;i++){
val = data.show(i);
for(int j=0;j<nchannels;j++){
T tmpval = val[j];
T tmpval2 = T(abs(tmpval));
What is that line for? You don't seem to be using 'tmpval2' at all...
result[j] += tmpval;
}
}
return result;
}
This works great for everything except for a personal wrapper I've
wrapped around complex numbers. Here's the first important bit of
mycomplex.h
file: mycomplex.h
#include <complex>
using namespace std;
OK, stop right there. Never, NEVER, have a "using namespace std;"
directive in a header. Such A BAD IDEA(tm) that I don't have words to
express it politely.
class mycomplex: public complex<double>{
If the whole point of 'using namespace' is to reduce typing from
'std::complex<double>' to 'complex<double>', then it's just wrong.
Instead, do (here)
typedef std::complex<double> cmplxd_t;
and use 'cmplxd_t' everywhere below.
Perhaps your problems will go away... Try it.
[..]
V
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