I am trying to write a template function which will extract the value of the given datatype from the given string. I came up with something like this:
template<class T>
static T getValue(const CString& val_in)
{
std::wstring value = val_in;
std::istringstream iss;
iss.str(value);
T val = T();
iss>>val;
return val;
}
But this gives the following error for the iss.str(value) statement.
error C2664: 'void
std::basic_istringstream<_Elem,_Traits,_Alloc>::str(const
std::basic_string<_Elem,_Traits,_Ax>
&)' : cannot convert parameter 1 from
'std::wstring' to 'const
std::basic_string<_Elem,_Traits,_Ax>
&'
So basically, std::istringstream is accepting only std::string . I thought there may be a std::wistringstream but there doesn't seem to be one available. Any clues how can I do it?
My compiler has wistringstream -- this is all it is:
typedef basic_istringstream<wchar_t> wistringstream;
Related
Here is the code:
vector<ClientInfo*> OpenRABiz::GetHumans() const {
vector<ClientInfo*> vec;
for (auto &c : clients) {
if (!c.isbot) {
vec.push_back(&c);
}
}
return vec; // RVO - return value optimization
}
In visual c++ 2019, compiler indate it:
error C2664: 'void std::vector<ClientInfo *,std::allocator<ClientInfo *>>::push_back(_Ty &&)': cannot convert argument 1 from 'const ClientInfo *' to 'const _Ty &'
The error message: "
const _Ty&" means the c++ template can't deduce the right parameters
.
When I take the const keyword, it compiles successfully.
vector<ClientInfo*> OpenRABiz::GetHumans()
Why?
Your clients is likely a vector of ClientInfo, so in a const-qualified member-functions, the type of client (in the loop) is const ClientInfo&. When you take the address &client, you get a const ClientInfo*, which cannot be converted to a ClientInfo*.
When you remove the const-qualifier, everything works fine because client is then ClientInfo&.
To fix the issue, change the return-type of the function and declaration of vec to std::vector<const ClientInfo*>.
This question already has answers here:
How do I implement a CString hash function for use with std::unordered_map?
(3 answers)
Closed 5 years ago.
I'm trying to create following unordered_map:
std::unordered_map<CString, CString, std::function<size_t(const CString &data)>> usetResponse(100, [](const CString &data)
{
return std::hash<std::string>()((LPCSTR)data);
});
I provided hash function for CString, but compiler still returns errors:
error C2338: The C++ Standard doesn't provide a hash for this type.
error C2664: 'std::unordered_map<CString,CString,std::hash<_Kty>,std::equal_to<_Kty>,std::allocator<std::pair<const
_Kty,_Ty>>>::unordered_map(std::initializer_list<std::pair<const _Kty,_Ty>>,unsigned int,const std::hash<_Kty> &,const _Keyeq &,const std::allocator<std::pair<const _Kty,_Ty>> &)' : cannot convert argument 1 from 'std::unordered_map<CString,CString,std::function<size_t (const CString &)>,std::equal_to<_Kty>,std::allocator<std::pair<const
_Kty,_Ty>>>' to 'const std::unordered_map<CString,CString,std::hash<_Kty>,std::equal_to<_Kty>,std::allocator<std::pair<const
_Kty,_Ty>>> &'
Please tell me what I'm doing wrong ?
Something like this:
struct CStringHash
{
size_t operator () (const CString &s) const
{
return hash<string>()(static_cast<LPCSTR>(s));
}
};
Then declare the map like this:
unordered_map<CString, CString, CStringHash> map;
I have declared Wstring as follows
wstring strID
When I try to find the occurrences sub-string as follows
int index = strID.find("LABS");
I am getting error like the following
error C2664: 'unsigned int std::basic_string<_Elem,_Traits,_Ax>::find(const std::basic_string<_Elem,_Traits,_Ax> &,unsigned int) const' : cannot convert parameter 1 from 'const char [13]' to 'const std::basic_string<_Elem,_Traits,_Ax> &'
Can you please help me to find the occurrences of sub-string?
When searching a wstring, you need to have the parameter as a wide string as well
int index = strID.find(L"LABS");
^
int index = strID.find(L"LABS");
EDIT:
http://msdn.microsoft.com/en-us/library/69ze775t(v=vs.80).aspx
I have made a test case to show the problems I am running into. Please forgive me my ignorance on the issues of Deferred libraries and pointer casting. The only library included in the deferred.lib.
#include <deferred/deferred.h>
using namespace deferred;
SafePtr<Deferred> recordTime(int time)
{
SafePtr<Deferred> d = createDeferred();
SafePtr<CallbackData> p = new PointerCBD< char>( 0 );
d->execute(p);
return d;
}
int main(int argc, char* argv[])
{
while(1)
{
SafePtr<Deferred> d = recordTime(1000);
d->waitHereForCompletion();
char* c = dynamic_pointer_cast<char>(d->endResult());
}
return 0;
}
When I try and compile in Windows XP with VS2008 I get:
Error C2440: 'initializing' : cannot convert from
'deferred:SafePtr' to 'char *' with
[T=char]
No user-defined-conversion operator available that can perform this
conversion, or the operator cannot be called.
I have tried this command to return a pointer, rather than a SafePtr:
ManagerTimings* t = dynamic_pointer_cast<ManagerTimings>(d->endResult()).get();
Then I get this error:
Error C2664: 'deferred::intrusive_ptr_release' : cannot convert
parameter 1 from 'char *' to
'deferred:ReferenceCountable *'
I have tried this command:
ManagerTimings* t = dynamic_pointer_cast<ManagerTimings>(d->endResult().get());
Then I get this error:
Error C2784: 'deferred::SafePtr deferred::dynamic_pointer_cast(const deferred::SafePtr< U > &)' : could not deduce template argument for 'const deferred::SafePtr< U > &' from 'deferred::CallbackData *'
Try this:
ManagerTimings* t = dynamic_pointer_cast<ManagerTimings>(d->endResult().get());
if you want to get an "unsafe" pointer, or probably this:
SafePtr<ManagerTimings> t= dynamic_pointer_cast<ManagerTimings>(d->endResult());
to get a safe ManagerTimings pointer. I don't know what library you are using, but I suspect that dynamic_pointer_cast can convert a SafePtr to another SafePtr. Or it just converts pointers.
&*d->endResult()
I think from this code endResult is the SafePtr you're having trouble with.
I am having a problem with command line parsing with boost:program_options. The quickest way to explain it is to show the code so:
const std::vector<tstring> args;
if (ac > 0 && NULL!=av) //ac is a ULONG
{
for (int i = 0; i < ac; i++)
{
args.push_back(av[i]); //av is an LPTSTR pointer (pointer to TCHAR*)
}
}
po::command_line_parser parser(args);
The parser ctor is supposed to take a const std::vector<charT>
typedef basic_command_line_parser<char> command_line_parser;
typedef basic_command_line_parser<wchar_t> wcommand_line_parser;
/** Creates instance of 'command_line_parser', passes parameters to it,
and returns the result of calling the 'run' method.
*/
template<class charT>
class basic_command_line_parser : private detail::cmdline {
public:
/** Creates a command line parser for the specified arguments
list. The 'args' parameter should not include program name.
*/
basic_command_line_parser(const std::vector<
std::basic_string<charT> >& args);
tstring in my program is
typedef std::basic_string<TCHAR> tstring;
The error I get is:
Error 16 error C2664: 'boost::program_options::basic_command_line_parser<charT>::basic_command_line_parser(const std::vector<_Ty> &)' : cannot convert parameter 1 from 'const std::vector<_Ty>' to 'const std::vector<_Ty> &' myfile.cpp 329
Where, oh where, am I going astray? I've tried all kinds of casting and re-defining, but nothing has worked and I'm at the end of my tether.
Edit #Zac:
Making the changes you suggested... I get the error:
Error 14 error C2664: boost::program_options::basic_command_line_parser<charT>::basic_command_line_parser(const std::vector<_Ty> &)' : cannot convert parameter 1 from 'std::vector<_Ty>' to 'const std::vector<_Ty> &' MyFile.cpp 328
Edit
Just to point out that I am using Visual Studio 2008 VC9 compiler
You seem to be using a unicode build, so either explicitly use the wide char version:
po::wcommand_line_parser parser(args);
or the more flexible:
po::basic_command_line_parser<TCHAR> parser(args);
The line you went astray with is below:
const std::vector<tstring> args;
Change it to:
std::vector<tstring> args;