tokeniterator.h

来自「很经典的书籍」· C头文件 代码 · 共 75 行

//: C07:TokenIterator.h
#ifndef TOKENITERATOR_H
#define TOKENITERATOR_H
#include <algorithm>
#include <cctype>
#include <functional>
#include <iterator>
#include <string>

struct Isalpha : std::unary_function<char, bool> {
  bool operator()(char c) {
    return std::isalpha(c);
  }
};

class Delimiters : std::unary_function<char, bool> {
  std::string exclude;
public:
  Delimiters() {}
  Delimiters(const std::string& excl)
    : exclude(excl) {}
  bool operator()(char c) {
    return exclude.find(c) == std::string::npos;
  }
};

template <class InputIter, class Pred = Isalpha>
class TokenIterator : public std::iterator<
    std::input_iterator_tag,std::string, std::ptrdiff_t> {
  InputIter first;
  InputIter last;
  std::string word;
  Pred predicate;
public:
  TokenIterator(InputIter begin, InputIter end,
    Pred pred = Pred())
    : first(begin), last(end), predicate(pred) {
      ++*this;
  }
  TokenIterator() {} // End sentinel
  // Prefix increment:
  TokenIterator& operator++() {
    word.resize(0);
    first = std::find_if(first, last, predicate);
    while (first != last && predicate(*first))
      word += *first++;
    return *this;
  }
  // Postfix increment
  class Proxy {
    std::string word;
  public:
    Proxy(const std::string& w) : word(w) {}
    std::string operator*() { return word; }
  };
  Proxy operator++(int) {
    Proxy d(word);
    ++*this;
    return d;
  }
  // Produce the actual value:
  std::string operator*() const { return word; }
  std::string* operator->() const {
    return &(operator*());
  }
  // Compare iterators:
  bool operator==(const TokenIterator&) {
    return word.size() == 0 && first == last;
  }
  bool operator!=(const TokenIterator& rv) {
    return !(*this == rv);
  }
};
#endif // TOKENITERATOR_H ///:~