学步园

STL的string已给我提供一些常用的算法(find，substr，erase，replace等)，但在实现应用中远远不能满足需求，像trim，toupper，tolower这样简单的算法都不提供，我曾偶发现一个开源的C++库中简洁优雅实现了这些算法。

1.trimLeft

template <class S><br /> S trimLeft(const S& str)<br /> /// Returns a copy of str with all leading<br /> /// whitespace removed.<br /> {<br /> typename S::const_iterator it = str.begin();<br /> typename S::const_iterator end = str.end();</p> <p> while (it != end && std::isspace(*it)) ++it;<br /> return S(it, end);<br /> }

2.trimLeftInPlace

template <class S><br /> S& trimLeftInPlace(S& str)<br /> /// Removes all leading whitespace in str.<br /> {<br /> typename S::iterator it = str.begin();<br /> typename S::iterator end = str.end();</p> <p> while (it != end && std::isspace(*it)) ++it;<br /> str.erase(str.begin(), it);<br /> return str;<br /> }  

3.trimRight

template <class S><br /> S trimRight(const S& str)<br /> /// Returns a copy of str with all trailing<br /> /// whitespace removed.<br /> {<br /> int pos = int(str.size()) - 1;</p> <p> while (pos >= 0 && std::isspace(str[pos])) --pos;<br /> return S(str, 0, pos + 1);<br /> }

4.trimRightInPlace

template <class S><br /> S& trimRightInPlace(S& str)<br /> /// Removes all trailing whitespace in str.<br /> {<br /> int pos = int(str.size()) - 1;</p> <p> while (pos >= 0 && std::isspace(str[pos])) --pos;<br /> str.resize(pos + 1);</p> <p> return str;<br /> }

5.trim

template <class S><br /> S trim(const S& str)<br /> /// Returns a copy of str with all leading and<br /> /// trailing whitespace removed.<br /> {<br /> int first = 0;<br /> int last = int(str.size()) - 1;</p> <p> while (first <= last && std::isspace(str[first])) ++first;<br /> while (last >= first && std::isspace(str[last])) --last;</p> <p> return S(str, first, last - first + 1);<br /> }

6.trimInPlace

template <class S><br /> S& trimInPlace(S& str)<br /> /// Removes all leading and trailing whitespace in str.<br /> {<br /> int first = 0;<br /> int last = int(str.size()) - 1;</p> <p> while (first <= last && std::isspace(str[first])) ++first;<br /> while (last >= first && std::isspace(str[last])) --last;</p> <p> str.resize(last + 1);<br /> str.erase(0, first);</p> <p> return str;<br /> }

7.toUpper

template <class S><br /> S toUpper(const S& str)<br /> /// Returns a copy of str containing all upper-case characters.<br /> {<br /> typename S::const_iterator it = str.begin();<br /> typename S::const_iterator end = str.end();</p> <p> S result;<br /> result.reserve(str.size());<br /> while (it != end) result += std::toupper(*it++);<br /> return result;<br /> }

8.toUpperInPlace

template <class S><br /> S& toUpperInPlace(S& str)<br /> /// Replaces all characters in str with their upper-case counterparts.<br /> {<br /> typename S::iterator it = str.begin();<br /> typename S::iterator end = str.end();</p> <p> while (it != end) { *it = std::toupper(*it); ++it; }<br /> return str;<br /> }

9.toLower

template <class S><br /> S toLower(const S& str)<br /> /// Returns a copy of str containing all lower-case characters.<br /> {<br /> typename S::const_iterator it = str.begin();<br /> typename S::const_iterator end = str.end();</p> <p> S result;<br /> result.reserve(str.size());<br /> while (it != end) result += std::tolower(*it++);<br /> return result;<br /> }

10.toLowerInPlace

template <class S><br /> S& toLowerInPlace(S& str)<br /> /// Replaces all characters in str with their lower-case counterparts.<br /> {<br /> typename S::iterator it = str.begin();<br /> typename S::iterator end = str.end();</p> <p> while (it != end) { *it = std::tolower(*it); ++it; }<br /> return str;<br /> }