C ++字符串上的<和>是否反映了字母顺序？

Question

I have a question about alphabetical order of strings in C++. Let us say i have two strings:

    string x="asd123";
    string y="asd136";

Can we compare these strings with < or > operators? For example: can we say

    if(x>y)
    cout<<".....";

Does that always work? Thanks.

Answer 1

The strings are compared lexicographically (dictionary style), with a string that's a shorter subset of another string coming before the longer one. But it's not necessarily alphabetical ; it's according to the underlying character encoding. Most systems these days use ASCII, so lowercase letters come out in order, and uppercase characters come out in order, and uppercase characters come before lowercase characters.

Answer 2

Yes, comparing std::string s with std::string::operator> always works. The strings are compared lexicographically . This means that each corresponding element of the two strings is compared in turn until two are found that are not equal, and that ordering determines the order of the strings.

The lexicographic ordering performs < on each element of the std::basic_string . That is, for a std::string , each char will be compared using < . It will simply compare the values of those char s. As far as C++ is concerned, a char is just a numeric value. These values are mapped to the characters in a string literal by the execution character set (which, for a modern C++ compiler, is almost always at least ASCII compatible).