On Thursday 22 April 2010 10:24:57 florent [dot] teichteil [..] ... wrote:
> Hi all
>
> The scripting language permits to concatenate strings, for instance:
> "firststring" + "secondstring" creates a new string with contents
> "firststringsecondstring". Yet, concatenating strings and ints as in C++
> is not enabled by default in RTT. To enable this feature, I am trying to
> extend the toolkit with the following C++ code:
>
> template <class T>
> struct string_numeric_concatenation : public
> std::binary_function<std::string, T, std::string> { std::string
> operator()(const std::string& s, T t) const {
> std::ostringstream oss(s);
> oss << t;
> return oss.str();
> }
> };

This looks wrong. The binary function inheritance should have different
template arguments, reflecting the arguments of operator():

template <class T>
struct string_numeric_concatenation 
 : public std::binary_function<std::string, const std::string&, T> { 
  std::string operator()(const std::string& s, T t) const {
 			std::ostringstream oss(s);
 			oss << t;
 			return oss.str();
  }
};

>
> Then I declare my new string concatenation operators:
>
> operators()->add(newBinaryOperator("+",
> string_numeric_concatenation<double>()));
> operators()->add(newBinaryOperator("+",
> string_numeric_concatenation<int>()));
>
> Nevertheless, when I try to concatenate "mystring" with 3 for instance, it
> does not work and I get the following warning:
>
> In Task Ressac[R]. (Status of last Command : none )
> (type 'ls' for context info) :"mystring" + 3
> Got :"mystring" + 3
> 814.101 [ Warning][Activity] Conversion from int to string
> = mystring

So this might be due to the wrong template ordering...

>
> Moreover, in big scripts, it seems the integer (3 for instance) randomly
> writes somewhere in forbidden memory locations. I am wondering what is
> happening here, since using ostringstreams to concatenate strings and
> numeric values is commonly used in C++ without problems. Does Orocos
> preprocess the integer before sending it to my concatenation operator?

No. What you wish for must be possible... Did you check your code with
valgrind ?

If it works, please submit a patch, I'll add it to the RTT.

Peter

Hi all

The scripting language permits to concatenate strings, for instance: "firststring" + "secondstring" creates a new string with contents "firststringsecondstring". Yet, concatenating strings and ints as in C++ is not enabled by default in RTT. To enable this feature, I am trying to extend the toolkit with the following C++ code:

template <class T>
struct string_numeric_concatenation : public std::binary_function<std::string, T, std::string> {
std::string operator()(const std::string& s, T t) const {
std::ostringstream oss(s);
oss << t;
return oss.str();
}
};

Then I declare my new string concatenation operators:

operators()->add(newBinaryOperator("+", string_numeric_concatenation<double>()));
operators()->add(newBinaryOperator("+", string_numeric_concatenation<int>()));

Nevertheless, when I try to concatenate "mystring" with 3 for instance, it does not work and I get the following warning:

In Task Ressac[R]. (Status of last Command : none )
(type 'ls' for context info) :"mystring" + 3
Got :"mystring" + 3
814.101 [ Warning][Activity] Conversion from int to string
= mystring

Moreover, in big scripts, it seems the integer (3 for instance) randomly writes somewhere in forbidden memory locations. I am wondering what is happening here, since using ostringstreams to concatenate strings and numeric values is commonly used in C++ without problems. Does Orocos preprocess the integer before sending it to my concatenation operator?

All the best,
Florent