C++ Part 20¶

#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
#include <ctime>
#include <numeric>
#include <cmath>
#include <sstream>
#include <thread>
#include <ctime>

#include <regex>

void PrintMatches(std::string str,
        std::regex reg){

    // Used when your searching a string
    std::smatch matches;

    // Determines if there is a match and match 
    // results are returned in matches
    while(std::regex_search(str, matches, reg)){

        // Get the first match
        std::cout << matches.str(1) << "\n";

        // Eliminate the previous match and create
        // a new string to search
        str = matches.suffix().str();
    }
    std::cout << "\n";
}

int main()
{   
    // Everything covered previously
    // [ ]   : Match what is in the brackets
    // [^ ]  : Match anything not in the brackets
    // .     : Match any 1 character or space
    // +     : Match 1 or more of what proceeds
    // \n    : Newline
    // \d    : Any 1 number
    // \D    : Anything but a number
    // \w    : Same as [a-zA-Z0-9_]
    // \W    : Same as [^a-zA-Z0-9_]
    // \s    : Same as [\f\n\r\t\v]
    // \S    : Same as [^\f\n\r\t\v]
    // {5}   : Match 5 of what proceeds the curly brackets
    // {5,7} : Match values that are between 5 and 7 in length
    // ()    : Return only what is between ()

    // ---------- MATCHING ZERO OR ONE ----------
    std::string str1 = "cat cats";
    std::regex reg1 ("([cat]+s?)");
    PrintMatches(str1, reg1);

    // ---------- MATCHING ZERO OR MORE ----------
    // * matches zero or more of what proceeds it

    std::string str2 = "doctor doctors doctor's";
    std::regex reg2 ("([doctor]+['s]{0,2})");
    PrintMatches(str2, reg2);

    // ---------- PROBLEM ----------
    //  On Windows newlines are some times \n and other times \r\n
    // Create a regex that will grab each of the lines in this
    // string, print out the number of matches and each line

    std::string str3 = "Just some words\n"
            "and some more\r\n"
            "and more\n";
    std::regex reg3 ("[\r]?\n");
    std::string line = std::regex_replace(str3, reg3, " ");
    std::cout << line << "\n";

    // ---------- GREEDY & LAZY MATCHING ----------

    // Let's try to grab everything between <name> tags
    // Because * is greedy (It grabs the biggest match possible)
    // we can't get what we want, which is each individual tag
    // match

    std::string str4 = "<name>Life On Mars</name>"
            "<name>Freaks and Geeks</name>";
    std::regex reg4 ("<name>(.*)</name>");
    PrintMatches(str4, reg4);

    // When we want to grab the smallest match we use *?, +?, or
    // {n,}? instead

    std::regex reg5 ("<name>(.*?)</name>");
    PrintMatches(str4, reg5);

    // ---------- WORD BOUNDARIES ----------

    // We use word boundaries to define where our matches start
    // and end

    // \\b matches the start or end of a word

    // If we want ape it will match ape and the beginning of apex
    std::string str6 = "ape at the apex";
    std::regex reg6 ("(ape)");
    PrintMatches(str6, reg6);

    // If we use a word boundary
    std::regex reg7 ("(\\bape\\b)");
    PrintMatches(str6, reg7);

    // ---------- STRING BOUNDARIES ----------

    // ^ : Matches the beginning of a string if outside of
    //     a [ ]
    // $ : Matches the end of a string

    // Grab everything from the start to the @
    std::string str8 = "Match everything up to @";
    std::regex reg8 ("(^.*[^@])");
    PrintMatches(str8, reg8);

    // Grab everything from @ to the end of the line
    std::string str9 = "@ Get this string";
    std::regex reg9 ("([^@\\s].*$)");
    PrintMatches(str9, reg9);

    // ---------- PROBLEM ----------

    // Get just the numbers minus the area codes from
    // this string

    std::string str10 = "206-709-3100 202-456-1111 212-832-2000";
    std::regex reg10 (".{3}-(.{8})");
    PrintMatches(str10, reg10);

    // ---------- MULTIPLE SUBEXPRESSIONS ----------
    // You can have multiple subexpressions as well
    // Get both numbers that follow 412 separately
    std::string str11 = "My number is 904-285-3700";
    std::regex reg11 ("(.{3})-(.*)-(.*)");
    std::smatch matches;
    if(std::regex_search(str11,matches,reg11)){
        for(int i = 1; i < matches.size(); i++){
            std::cout << matches[i] << "\n";
        }
    }

    return 0; }