Strings ( string )

Definition

An instance s of the data type string is a sequence of characters (type char). The number of characters in the sequence is called the length of s. A string of length zero is called the empty string. Strings can be used wherever a C++ const char* string can be used.

Strings differ from the C++ type char* in several aspects: parameter passing by value and assignment works properly (i.e., the value is passed or assigned and not a pointer to the value) and strings offer many additional operations.

#include < LEDA/core/string.h >

Types

string::size_type

the size type.

Creation

string	s	introduces a variable s of type string. s is initialized with the empty string.
string	s(const char* p)	introduces a variable s of type string. s is initialized with a copy of the C++ string p.
string	s(char c)	introduces a variable s of type string. s is initialized with the one-character string ``c''.
string	s(const char* format, ...)
		introduces a variable s of type string. s is initialized with the string produced by printf(format,...).

Operations

int	s.length()	returns the length of string s.
bool	s.empty()	returns whether s is the empty string.
char	s.char_at(int i)	returns the character at position i. Precondition 0 < = i < = s.length()-1.
char	s[int i]	returns s.char$\_$at(i).
char&	s[int i]	returns a reference to the character at position i. Precondition 0 < = i < = s.length()-1.
string	s.substring(int i, int j)	returns the substring of s starting at position max(0, i) and ending at position min(j, s.length()) - 1.
string	s.substring(int i)	returns the substring of s starting at position max(0, i).
string	s(int i, int j)	returns the substring of s starting at position max(0, i) and ending at position min(j, s.length()-1). If min(j, s.length() -1) < max(0, i) then the empty string is returned.
string	s.head(int i)	returns the first i characters of s if i > = 0 and the first ( length() + i) characters of s if i < 0.
string	s.tail(int i)	returns the last i characters of s if i > = 0 and the last ( length() + i) characters of s if i < 0.
int	s.index(string x, int i)	returns the minimum j such that j > = i and x is a substring of s starting at position j (returns -1 if no such j exists).
int	s.index(const string& x)	returns s.index(x, 0).
int	s.index(char c, int i)	returns the minimum j such that j > = i and s[j] = c (-1 if no such j exists).
int	s.index(char c)	returns s.index(c, 0).
int	s.last_index(string x, int i)
		returns the maximum j such that j < = i and x is a substring of s starting at position j (returns -1 if no such j exists).
int	s.last_index(const string& x)
		returns s.last_index (x, s.length() - 1).
int	s.last_index(char c, int i)
		returns the maximum j such that j < = i and s[j] = c (-1 if no such j exists).
int	s.last_index(char c)	returns s.last_index (c, s.length() - 1).
string	s.next_word(int& i, char sep)
		returns word (substring separated by sep characters) starting at index i and assigns start of next word to i (-1 if not existing).
int	s.split(string* A, int sz, char sep=-1)
		splits s into substrings separated by sep characters or white space (if sep = - 1) and stores them in the array A[0..sz - 1]. The operation returns the number of created substrings (at most sz). PreconditionA is an array of length sz.
int	s.count_words(char sep=-1)
		returns the number of substrings separated by sep characters or white space (if sep = - 1).
int	s.break_into_words(string* A, int sz)
		breaks s into words separated by white space characters and stores them in the array A. Same as s.split(A, sz, - 1)
string	s.expand_tabs(int tab_w)	return the result of expanding all tabs in s using tabulator width tab$\_$w.
bool	s.contains(const string& x)
		true iff x is a substring of s.
bool	s.starts_with(const string& x)
		true iff s starts with x.
bool	s.begins_with(const string& x)
		true iff s starts with x.
bool	s.ends_with(const string& x)
		true iff s starts with x.
string	s.insert(int i, string x)	returns s(0, i - 1) + s1 + s(i, s.length()-1).
string	s.replace(const string& s1, const string& s2, int i=1)
		returns the string created from s by replacing the i-th occurrence of s1 in s by s2. Remark: The occurences of s1 in s are counted in a non-overlapping manner, for instance the string sasas contains only one occurence of the string sas.
string	s.replace(int i, int j, const string& x)
		returns the string created from s by replacing s(i, j) by x. Preconditioni < = j.
string	s.replace(int i, const string& x)
		returns the string created from s by replacing s[i] by x.
string	s.replace_all(const string& s1, const string& s2)
		returns the string created from s by replacing all occurrences of s1 in s by s2. PreconditionThe occurrences of s1 in s do not overlap (it's hard to say what the function returns if the precondition is violated.).
string	s.del(const string& x, int i=1)
		returns s.replace(x,"", i).
string	s.del(int i, int j)	returns s.replace(i, j,"").
string	s.del(int i)	returns s.replace(i,"").
string	s.del_all(const string& x)
		returns s.replace_all(x,"").
void	s.read(istream& I, char delim = ' ')
		reads characters from input stream I into s until the first occurrence of character delim. (If delim is ' \ n' it is extracted from the stream, otherwise it remains there.)
void	s.read(char delim = ' ')	same as s.read(cin,delim).
void	s.read_line(istream& I)	same as s.read(I,' \ n').
void	s.read_line()	same as s.read_line(cin).
void	s.read_file(istream& I)	same as s.read(I,'EOF').
void	s.read_file()	same as s.read_file(cin).
string&	s += const string& x	appends x to s and returns a reference to s.
string	const string& x + const string& y
		returns the concatenation of x and y.
bool	const string& x == const string& y
		true iff x and y are equal.
bool	const string& x != const string& y
		true iff x and y are not equal.
bool	const string& x < const string& y
		true iff x is lexicographically smaller than y.
bool	const string& x > const string& y
		true iff x is lexicographically greater than y.
bool	const string& x <= const string& y
		returns (x < y) | (x = = y).
bool	const string& x >= const string& y
		returns (x > y) | (x = = y).
istream&	istream& I » string& s	same as s.read(I,' ').
ostream&	ostream& O « const string& s
		writes string s to the output stream O.

Iteration

forall_words(x, s) { ``the words of s are successively assigned to x'' }

forall_lines(x, s) { ``the lines of s are successively assigned to x'' }

Implementation

Strings are implemented by C++ character vectors. All operations involving the search for a pattern x in a string s take time O(s.lenght()*x.length()), [ ] takes constant time and all other operations on a string s take time O(s.length()).