vector representation

[Andrea Crotti]

I have the following problem, I have a vector of chars and I want to
represent it as
a vector of ints.
So I added another parameter in the template function which defaults
to T (gcc needs the new 0++x standard for this) but still it doesn't
work

Here below the code, the function at run time is correct
"vectorToString<char, unsigned int>"
but I always see printed out the char representation.
Anything else wrong?


template <typename T, typename Repr=T>
std::string vectorToString(const std::vector<T>& inp) {
std::string empty("[]");
if (inp.size() == 0)
return empty;

std:stringstream os;
os << "[";
size_t i;
for (i=0; i < (inp.size()-1); ++i) {
os << static_cast<Repr> (inp) << ",";
}
os << static_cast<Repr> (inp) << "]";
return os.str();
}


Thanks,
Andrea

 

[Ian Collins]

I have the following problem, I have a vector of chars and I want to
represent it as
a vector of ints.
So I added another parameter in the template function which defaults
to T (gcc needs the new 0++x standard for this) but still it doesn't
work

Here below the code, the function at run time is correct
"vectorToString<char, unsigned int>"
but I always see printed out the char representation.
Anything else wrong?


template<typename T, typename Repr=T>

Function template default parameters are a C++0x feature.

std::string vectorToString(const std::vector<T>& inp) {
std::string empty("[]");
if (inp.size() == 0)
return empty;

std:stringstream os;
os<< "[";
size_t i;
for (i=0; i< (inp.size()-1); ++i) {
os<< static_cast<Repr> (inp)<< ",";
}
os<< static_cast<Repr> (inp)<< "]";
return os.str();
}

What doesn't work? I tried this with gcc 4.5.1:

int main()
{
std::vector<char> v {'a', 'b','c'};

std::cout << vectorToString<char,unsigned int>( v ) << std::endl;
}

and it gives the expected

[97,98,99]

 

[Paul]

I have the following problem, I have a vector of chars and I want to
represent it as
a vector of ints.
So I added another parameter in the template function which defaults
to T (gcc needs the new 0++x standard for this) but still it doesn't
work

What do you mean by "represented as a vector of int"?

Does the char array "A" == 65? In other words a direct ascii conversion
Does the char array "65" == two integers (6 & 5), or one int(65).
Whats happens if you have "65.6"? Is it rounded up ?

Conversion from string to vector of int aint so simple I know you say
"vector of char" above but your code below uses strings, so I dunno if chars
are treated individually or as strings.

Here below the code, the function at run time is correct
"vectorToString<char, unsigned int>"
but I always see printed out the char representation.
Anything else wrong?

Output to screen is always going to be chars. How can it be anything else?

Maybe its better to assign to a vector of int, and examine this in a
debugger , for testing purposes. Screen output can introduce another
conversion.

template <typename T, typename Repr=T>
std::string vectorToString(const std::vector<T>& inp) {
std::string empty("[]");
if (inp.size() == 0)
return empty;

std:stringstream os;
os << "[";
size_t i;
for (i=0; i < (inp.size()-1); ++i) {
os << static_cast<Repr> (inp) << ",";
}
os << static_cast<Repr> (inp) << "]";
return os.str();
}


Thanks,
Andrea

 

[Andrea Crotti]

What doesn't work?  I tried this with gcc 4.5.1:

int main()
{
   std::vector<char> v {'a', 'b','c'};

   std::cout << vectorToString<char,unsigned int>( v ) << std::endl;

}

and it gives the expected

[97,98,99]

Ah ok, well that's not what I meant, that's why it probably doesn't
"work" for me..
I just want to have something like
std::vector<char> v{1, 2, 3};
and print out
[1, 2, 3]
instead of the char corresponding to 1, 2, 3 in the ASCII table, which
is what happens now..

 

[Andrea Crotti]

Alright I tried like this

#include <iostream>
#include <ostream>
#include <string>
#include <vector>
#include <sstream>


template<typename T, typename Repr=T>
std::string vectorToString(const std::vector<T>& inp) {
std::string empty("[]");
if (inp.size() == 0)
return empty;
std:stringstream os;
os<< "[";
size_t i;
for (i=0; i< (inp.size()-1); ++i) {
os<< static_cast<Repr> (inp)<< ",";
}
os<< static_cast<Repr> (inp)<< "]";
return os.str();
}

int main()
{
std::vector<char> v {1, 2, 3};
std::cout << vectorToString<char,unsigned int>( v ) << std::endl;
}

and then yes, it's correct already, I'm probably doing something else
stupid when calling the function then...
Thanks

 

[Paul]

Alright I tried like this

#include <iostream>
#include <ostream>
#include <string>
#include <vector>
#include <sstream>


template<typename T, typename Repr=T>
std::string vectorToString(const std::vector<T>& inp) {
std::string empty("[]");
if (inp.size() == 0)
return empty;
std:stringstream os;
os<< "[";
size_t i;
for (i=0; i< (inp.size()-1); ++i) {
os<< static_cast<Repr> (inp)<< ",";
}
os<< static_cast<Repr> (inp)<< "]";
return os.str();
}

int main()
{
std::vector<char> v {1, 2, 3};
std::cout << vectorToString<char,unsigned int>( v ) << std::endl;
}

and then yes, it's correct already, I'm probably doing something else
stupid when calling the function then...
Thanks

If you want to convert to a vector of int , why do you return a string?
The conversion is only temporary and you do not see what its converted to,
what you need to do is something like this :

#include <iostream>
#include <string>
#include <vector>

template< template<typename T1, typename Alloc1> class C1, typename T1,
typename Alloc1,
template<typename T2, typename Alloc2> class C2, typename T2, typename
Alloc2>
void convert(const C1<T1, Alloc1>& vchar, C2<T2, Alloc2>& vint) {
for (std::size_t i=0; i<vchar.size(); ++i){
vint = 0xF & static_cast<T2>(vchar);
/*Mask the ascii value with 0xF to convert to int.*/
}
}

int main()
{
std::vector<char> vc(3);
vc[0]='1';
vc[1]='2';
vc[2]='3';
std::vector<int> vi(3);

convert(vc, vi);

for (int i=0;i<3; ++i ){
std::cout<< vi <<'\t';
}

}

 

[Andrea Crotti]

If you want to convert to a vector of int , why do you return a string?
The conversion is only temporary and you do not see what its converted to,
what you need to do is something like this :

#include <iostream>
#include <string>
#include <vector>

template< template<typename T1, typename Alloc1> class C1, typename T1,
typename Alloc1,
template<typename T2, typename Alloc2> class C2, typename T2, typename
Alloc2>
void convert(const C1<T1, Alloc1>& vchar, C2<T2, Alloc2>& vint) {
    for (std::size_t i=0; i<vchar.size(); ++i){
  vint = 0xF & static_cast<T2>(vchar);
/*Mask the ascii value with 0xF to convert to int.*/
    }

}

int main()
{
    std::vector<char> vc(3);
 vc[0]='1';
 vc[1]='2';
 vc[2]='3';
 std::vector<int> vi(3);

    convert(vc, vi);

 for (int i=0;i<3; ++i ){
  std::cout<< vi <<'\t';
 }

}

Thanks, but actually I don't need to convert (in this case I have
already conversions for other cases...).
I just want to use only one integer using 1 byte only, since I don't
need more.

So probably the solution of my problem could be simply to use this
typedef uint8_t hop_count_t;

and it might work already (even if now I get other errors, probably I
hardwired an int by mistake somewhere..)