Reputation: 2088
I am trying to read a long text, and am to separate this text into every word it contains. The first attempt I made was reading it from a file using std::ifstream
and the operator>>
to read into a string. The problem is, since it only cuts text on whitespace characters, I still get periods at the last word of a phrase (like problem.
) and some special strings that don't mean nothing (sometimes I have ->
or **
).
I thought on reading char by char, or splitting the string read char by char too, and finding removing the characters that aren't in the correct range (something between a-z, A-Z and 0-9), but this solution seems very messed up. Also, I could not use regular expressions since I'm using GCC 4.8.3 and it is not possible to use Boost.
Is there a better solution than this second one, or is this the good way? By good I mean relatively easy to implement and yielding the expected result (only alphanumeric characters).
Upvotes: 1
Views: 94
Reputation:
You might install a custom ctype in your stream locale:
#include <iostream>
#include <locale>
#include <sstream>
class WordCharacterClassification : public std::ctype<char>
{
private:
typedef std::ctype<char> Base;
const mask* initialize_table(const Base&);
public:
typedef Base::mask mask;
typedef Base::char_type char_type;
public:
WordCharacterClassification(const Base& source, std::size_t refs = 0)
: Base(initialize_table(source), false, refs)
{}
private:
mask m_table[Base::table_size];
};
inline const typename WordCharacterClassification::mask*
WordCharacterClassification::initialize_table(const Base& source) {
const mask* src = source.table();
const mask* src_end = src + Base::table_size;
const mask space
= std::ctype_base::space
| std::ctype_base::cntrl
| std::ctype_base::digit
| std::ctype_base::punct;
mask* dst = m_table;
for( ; src < src_end; ++dst, ++src) {
*dst = *src;
if(*src & space)
*dst |= std::ctype_base::space;
}
return m_table;
}
int main() {
std::istringstream in("This->is a delimiter-test4words");
std::locale locale = in.getloc();
WordCharacterClassification classification(
std::use_facet<std::ctype<char>>(locale),
// We hold a reference and do not transfer ownership:
true);
in.imbue(std::locale(locale, &classification));
std::string word;
std::cout << "Words:\n";
while(in >> word) {
std::cout << word << '\n';
}
}
Note: A static table (without copying an original) would simplify it.
Upvotes: 1
Reputation: 2424
Your second solution would be a implementation and probably help you learn how to handle input. You could handle each character based on isalpha (http://www.cplusplus.com/reference/cctype/isalpha/). Where anything returning false would immediately end "this current word" and start on the next word.
Upvotes: 0