SYNOPSIS

DESCRIPTION

The Pattern class supports the use of the following (Perl-like) special escape sequences:
\b - indicating a word-boundary
\d - indicating a digit ([[:digit:]]) character
\s - indicating a white-space ([:space:]) character
\w - indicating a word ([:alnum:]) character

The corresponding capitals (e.g., \W) define the complementary character sets. The capitalized character set shorthands are not expanded inside explicit character-classes (i.e., [ ... ] constructions). So [\W] represents a set of two characters: \ and W.

As the backslash (\) is treated as a special character it should be handled carefully. Pattern converts the escape sequences \d \s \w (and outside of explicit character classes the sequences \D \S \W) to their respective character classes. All other escape sequences are kept as is, and the resulting regular expression is offered to the pattern matching compilation function regcomp(3). This function will again interpret escape sequences. Consequently some care should be exercised when defining patterns containing escape sequences. Here are the rules:

• Special escape sequences (like \d) are converted to character classes. E.g.,

      ---------------------------------------------------------
      Specify:    Converts to:    regcomp uses:      Matches:
      ---------------------------------------------------------
      \d          [[:digit:]]     [[:digit:]]        3
      ---------------------------------------------------------
          
  

• Ordinary escape sequences (like \x) are kept as-is. E.g.,

      ---------------------------------------------------------
      Specify:    Converts to:    regcomp uses:      Matches:
      ---------------------------------------------------------
      \x          \x              x                  x
      ---------------------------------------------------------
          
  

• To specify a literal escape sequence, it must be written twice. E.g.,

      ---------------------------------------------------------
      Specify:    Converts to:    regcomp uses:      Matches:
      ---------------------------------------------------------
      \\x         \\x             \x                 \x
      ---------------------------------------------------------
          
  

NAMESPACE

INHERITS FROM

TYPEDEF

• Pattern::Position:
  A nested type representing the offsets of the first character and the offset beyond the last character of the matched text or indexed subexpression, defined as std::pair<std::string::size_type, std::string::size_type>.

CONSTRUCTORS

o

Pattern():
The default constructor defines no pattern, but is available as a placeholder for, e.g., containers requiring default constructors. A Pattern object thus constructed cannot be used to match patterns, but can be the lvalue in assignments where another Pattern object is the rvalue. However, it can receive a pattern using the member setPattern() (see below). An FBB::Exception object is thrown if the object could not be constructed.

o

Pattern(std::string const &pattern, bool caseSensitive = true, size_t nSub = 10, int options = REG_EXTENDED | REG_NEWLINE):
This constructor compiles pattern, preparing the Pattern object for pattern matches. The second parameter determines whether case sensitive matching will be used (the default) or not. Subexpressions are defined by parentheses pairs. Each matching pair defines a subexpression, where the order-number of their opening parentheses determines the subexpression's index. By default at most 10 subexpressions are recognized. The options flags may be:

REG_EXTENDED:
Use POSIX Extended Regular Expression syntax when interpreting regex. If not set, POSIX Basic Regular Expression syntax is used.

REG_NOSUB:
Support for substring addressing of matches is not required. The nmatch and pmatch parameters to regexec are ignored if the pattern buffer supplied was compiled with this flag set.

REG_NEWLINE:
Match-any-character operators don't match a newline.

A non-matching list ([^...]) not containing a newline does not match a newline.

Match-beginning-of-line operator (^) matches the empty string immediately after a newline, regardless of whether eflags, the execution flags of regexec, contains REG_NOTBOL.

Match-end-of-line operator ($) matches the empty string immediately before a newline, regardless of whether eflags contains REG_NOTEOL.

Pattern offers copy and move constructors.

MEMBER FUNCTIONS

• std::string before() const:
  Following a successful match, before() returns the text before the matched text.
• std::string beyond() const:
  Following a successful match, beyond() returns the text beyond the matched text.
• size_t end() const:
  Returns the number of matched elements (text and subexpressions). end() is the lowest index value for which position() returns two std::string::npos values (see the position() member function, below).
• void match(std::string const &text, int options = 0):
  Match a string with a pattern. If the text could not be matched, an Exception exception is thrown , using Pattern::match() as its prefix-text.
• Options may be:
• REG_NOTBOL:
  The match-beginning-of-line operator always fails to match (but see the compilation flag REG_NEWLINE above) This flag may be used when different portions of a string are passed to regexec and the beginning of the string should not be interpreted as the beginning of the line.
• REG_NOTEOL:
  The match-end-of-line operator always fails to match (but see the compilation flag REG_NEWLINE)
• std::string matched() const:
  Following a successful match, this function returns the matched text.
• std::string const &pattern() const:
  This member function returns the pattern that is offered to regcomp(3). It returns the contents of a static string that is overwritten at each construction of a Pattern object and at each call of the setPattern() member function.
• Pattern::Position position(size_t index) const:
  With index == 0 the fully matched text is returned (identical to matched()). Other index values return the corresponding subexpressions. std::string::npos, std::string::npos is returned if index is at least end() (which may happen at index value 0).
• void setPattern(std::string const &pattern, bool caseSensitive = true, size_t nSub = 10, int options = REG_EXTENDED | REG_NEWLINE):
  This member function installs a new compiled pattern in its Pattern object. This member's parameters are identical to the second constructor's parameters. Refer to that constructor for details about the parameters. Like the constructor, an FBB::Exception exception is thrown if the new pattern could not be compiled.
• void swap(Pattern &other):
  The contents of the current object and the other object are swapped.

OVERLOADED OPERATORS

• Pattern &operator=(Pattern &other):
  A standard overloaded assignment operator.
• std::string operator[](size_t index) const:
  Returns the matched text (for index 0) or the text of a subexpression. An empty string is returned for index values which are at least end().
• Pattern &operator<<(int matchOptions):
  Defines match-options to be used with the following overloaded operator.
• bool operator<<(std::string const &text):
  Performs a match(text, matchOptions) call, catching any exception that might be thrown. If no matchOptions were set using the above overloaded operator, none are used. The options set this way are not `sticky': when necessary, they have to be re-inserted before each new pattern matching. The function returns true if the matching was successful, false otherwise.

EXAMPLE

/*
                              driver.cc
*/
#include "driver.h"
#include <bobcat/pattern>
using namespace std;
using namespace FBB;
void showSubstr(string const &str)
{
    static int 
        count = 1;
    cout << "String " << count++ << " is '" << str << "'\n";
}
int main(int argc, char **argv)
{
    {
        Pattern one("one");
        Pattern two(one);
        Pattern three("a");
        Pattern four;
        three = two;
    }
    try 
    {
        Pattern pattern("aap|noot|mies");
        {
            Pattern extra(Pattern(pattern));
        }
    
        if (pattern << "noot")
            cout << "noot matches\n";
        else
            cout << ": noot doesn't match\n";
    }
    catch (exception const &e)
    {
        cout << e.what() << ": compilation failed" << endl;
    }
        
    string pat = "\\d+";
    while (true)
    {
        cout << "Pattern: '" << pat << "'\n";
        try
        {
            Pattern patt(pat, argc == 1);   // case sensitive by default,
                                            // any arg for case insensitive
            cout << "Compiled pattern: " << patt.pattern() << endl;
            Pattern pattern;
            pattern = patt;                 // assignment operator
            while (true)
            {
                cout << "string to match : ";
                string st;
                getline(cin, st);
                if (st == "")
                    break;
                cout << "String: '" << st << "'\n";
                try
                {
                    pattern.match(st);
                    Pattern p3(pattern);
        
                    cout << "before:  " << p3.before() << "\n"
                            "matched: " << p3.matched() << "\n"  
                            "beyond:  " << pattern.beyond() << "\n"  
                            "end() = " << pattern.end() << endl;
        
                    for (size_t idx = 0; idx < pattern.end(); ++idx)
                    {
                        string str = pattern[idx];
            
                        if (str == "")
                            cout << "part " << idx << " not present\n";
                        else
                        {
                            Pattern::Position pos = pattern.position(idx);
        
                            cout << "part " << idx << ": '" << str << "' (" <<
                                    pos.first << "-" << pos.second << ")\n";
                        }
                    }
                }
                catch (exception const &e)
                {
                    cout << e.what() << ": " << st << " doesn't match" << endl;
                    continue;
                }
            }
        }            
        catch (exception const &e)
        {
            cout << e.what() << ": compilation failed" << endl;
        }
        cout << "New pattern: ";
        if (!getline(cin, pat) || !pat.length())
            return 0;
    }
}

FILES

DISTRIBUTION FILES

• bobcat_4.02.00-x.dsc: detached signature;
• bobcat_4.02.00-x.tar.gz: source archive;
• bobcat_4.02.00-x_i386.changes: change log;
• libbobcat1_4.02.00-x_*.deb: debian package holding the libraries;
• libbobcat1-dev_4.02.00-x_*.deb: debian package holding the libraries, headers and manual pages;
• http://sourceforge.net/projects/bobcat: public archive location;

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