Separator character in string c++

Question

This is the requirement: Read a string and loop it, whenever a new word is encountered insert it into std::list. If the . character has a space, tab, newline or digit on the left and a digit on the right then it is treated as a decimal point and thus part of a word. Otherwise it is treated as a full stop and a word separator.

And this is the result I run from the template program:

foo.bar -> 2 words (foo, bar)
f5.5f -> 1 word
.4.5.6.5 -> 1 word
d.4.5f -> 3 words (d, 4, 5f)
.5.6..6.... -> 2 words (.5.6, 6)

It seems very complex for me in first time dealing with string c++. Im really stuck to implement the code. Could anyone suggest me a hint ? Thanks

I just did some scratch ideas

bool isDecimal(std::string &word) {
    bool ok = false;
    for (unsigned int i = 0; i < word.size(); i++) {
        if (word[i] == '.') {
            if ((std::isdigit(word[(int)i - 1]) || 
                 std::isspace(word[(int)i -1]) || 
                 (int)(i - 1) == (int)(word.size() - 1)) && std::isdigit(word[i + 1]))
                ok = true;
            else {
                ok = false;
                break;
            }
        }
    }
    return ok;
}
    void checkDecimal(std::string &word) {
    if (!isDecimal(word)) {
        std::string temp = word;
        word.clear();
        for (unsigned int i = 0; i < temp.size(); i++) {
            if (temp[i] != '.')
                word += temp[i];
            else {
                if (std::isalpha(temp[i + 1]) || std::isdigit(temp[i + 1]))
                    word += ' ';
            }
        }
    }
    trimLeft(word);
}

Answer 1

I think you may be approaching the problem from the wrong direction. It seems much easier if you turn the condition upside down. To give you some pointers in a pseudocode skeleton:

bool isSeparator(const std::string& string, size_t position)
{
    // Determine whether the character at <position> in <string> is a word separator
}

void tokenizeString(const std::string& string, std::list& wordList)
{
    // for every character in string
        // if(isSeparator(character) || end of string)
            // list.push_back(substring from last separator to this one)
}

Answer 2

我建议使用flex和bison以及c ++实现来实现它