std::basic_string::compare
From cppreference.com
< cpp | string | basic string
int compare( const basic_string& str ) const;
|
(1) | |
int compare( size_type pos1, size_type count1,
const basic_string& str ) const; |
(2) | |
(3) | ||
int compare( size_type pos1, size_type count1,
const basic_string& str, |
(until C++14) | |
int compare( size_type pos1, size_type count1,
const basic_string& str, |
(since C++14) | |
int compare( const CharT* s ) const;
|
(4) | |
int compare( size_type pos1, size_type count1,
const CharT* s ) const; |
(5) | |
int compare( size_type pos1, size_type count1,
const CharT* s, size_type count2 ) const; |
(6) | |
Compares two character sequences.
1) Compares this string to str. First, calculates the number of characters to compare, as if by size_type rlen = std::min(size(), str.size()). Then compares by calling Traits::compare(data(), str.data(), rlen). For standard strings this function performs character-by-character lexicographical comparison. If the result is zero (the strings are equal so far), then their sizes are compared as follows:
Condition | Result | Return value | |
---|---|---|---|
Traits::compare(data, arg, rlen) < 0
|
data is less than arg | <0 | |
Traits::compare(data, arg, rlen) == 0
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size(data) < size(arg)
|
data is less than arg | <0 |
size(data) == size(arg)
|
data is equal to arg | 0 | |
size(data) > size(arg)
|
data is greater than arg | >0 | |
Traits::compare(data, arg, rlen) > 0
|
data is greater than arg | >0 |
2) Compares a
[pos1, pos1+count1)
substring of this string to str as if by basic_string(*this, pos1, count1).compare(str)
3) Compares a
[pos1, pos1+count1)
substring of this string to a substring [pos2, pos2+count2)
of str as if by basic_string(*this, pos1, count1).compare(basic_string(str, pos2, count2))
4) Compares this string to the null-terminated character sequence beginning at the character pointed to by s, as if by compare(basic_string(s))
5) Compares a
[pos1, pos1+count1)
substring of this string to the null-terminated character sequence beginning at the character pointed to by s, as if by basic_string(*this, pos, count1).compare(basic_string(s))
6) Compares a
[pos1, pos1+count1)
substring of this string to the first count2
characters of the character array whose first character is pointed to by s, as if by basic_string(*this, pos, count1).compare(basic_string(s, count2)). (Note: the characters from s
to s+count2
may include null characters))
Contents |
[edit] Parameters
str | - | other string to compare to |
s | - | pointer to the character string to compare to |
count1 | - | number of characters of this string to compare |
pos1 | - | position of the first character in this string to compare |
count2 | - | number of characters of the given string to compare |
pos2 | - | position of the first character of the given string to compare |
[edit] Return value
negative value if *this appears before the character sequence specified by the arguments, in lexicographical order
zero if both character sequences compare equivalent
positive value if *this appears after the character sequence specified by the arguments, in lexicographical order
[edit] Exceptions
1)
(none) | (until C++11) |
noexcept specification: noexcept |
(since C++11) |
2-6) May throw the exceptions thrown by the corresponding
basic_string
constructors.[edit] Possible implementation
template<class CharT, class Traits, class Alloc> int basic_string<CharT, Traits, Alloc>::compare(const std::basic_string& s) const noexcept { size_type lhs_sz = size(); size_type rhs_sz = s.size(); int result = traits_type::compare(data(), s.data(), std::min(lhs_sz, rhs_sz)); if (result != 0) return result; if (lhs_sz < rhs_sz) return -1; if (lhs_sz > rhs_sz) return 1; return 0; } |
[edit] Notes
For the situations when three-way comparison is not required, std::basic_string provides the usual relational operators (<
, <=
, ==
, >
, etc).
By default (with the default std::char_traits), this function is not locale-sensitive. See std::collate::compare for locale-aware three-way string comparison.
[edit] Example
This section is incomplete Reason: no example |
[edit] See also
lexicographically compares two strings (function template) |
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returns a substring (public member function) |
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defines lexicographical comparison and hashing of strings (class template) |
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compares two strings in accordance to the current locale (function) |
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returns true if one range is lexicographically less than another (function template) |