I am trying to come up with a case insensitive string, and I found the following on the web
http://www.gotw.ca/gotw/029.htm
So basically my code to come up with a case insensitive string is as follows
struct ci_char_traits : public std::char_traits<char> {
static bool eq( char c1, char c2 )
{ return toupper(c1) == toupper(c2); }
static bool ne( char c1, char c2 )
{ return toupper(c1) != toupper(c2); }
static bool lt( char c1, char c2 )
{ return toupper(c1) < toupper(c2); }
static int compare(const char* s1, const char* s2, size_t n )
{ return memicmp( s1, s2, n ); }
private:
static int memicmp(const void *s1, const void *s2, size_t n) {
if (n != 0) {
const unsigned char *p1 = (const unsigned char *)s1, *p2 = (const unsigned char *)s2;
do {
if (toupper(*p1) != toupper(*p2))
return (*p1 - *p2);
p1++;
p2++;
} while (--n != 0);
}
return 0;
}
};
// case insensitive string type definition
typedef std::basic_string<char, ci_char_traits> ci_string;
// provide standard output for case insensitive string
template<typename char_type, typename traits_type, typename allocator_type>
inline std::basic_ostream<char_type, traits_type>&
operator<<(std::basic_ostream<char_type, traits_type>& os,
const std::basic_string<char_type, ci_char_traits, allocator_type>& str) {
return std::__ostream_insert(os, str.data(), str.size());
}
so the type definition is the string. Now the problem I have, is that I can't get a function to work with this custom string as it works with a regular string. The following template function gets a value from the string, but the
template <typename T, class string_type, typename counter_type>
T stream_cast(const string_type& s) {
typedef typename string_type::value_type char_type;
typedef typename string_type::traits_type traits_type;
typename std::basic_istringstream<char_type, traits_type> iss(s);
T x;
char c;
if (!(iss >> x) || iss.get(c))
cout<<"*** ERROR *** Bad Conversion!"<<endl;
return x;
}
I call this function to get a double from a string as follows:
ci_string str("2.0");
double test = stream_cast<double>(str);
But something is wrong with my definition of case insensitive string because the evaluation of the stream object through operator! always fails (the line !(iss >> x) is always true for this string type).
Does someone know why I'm having this problem? Thanks in advance for taking the time to read this long post.
aa
You wrote a custom output operator "operator>>", but not an input operator "operator<<", and that's the one you need.
This works great:
ci_string str("2.0");
std::cout << str << std::endl;
because of the operator>>.
But
std::cin >> str
does not.