Repetition in Regular Expressions

jrobertson (James Robertson) — Sat, 02 Feb 2008 13:56:11 GMT

This irb session example helps demonstrate repetition in regular expressions using * ? + {}

Definitions:

? - the preceding token is optional
+ - find the token 1 or more times
* - find the token 0 or more times
{n} - repeat the token n no of times



irb(main):058:0> "this song is my favourite"[/favou?rite/]

=> "favourite"

irb(main):059:0> "this song is my favorite"[/favou?rite/]

=> "favorite"



irb(main):100:0> "this is my favourite\s"[/this\s((song|video)\s)?is/]

=> "this is"

irb(main):101:0> "this song is my favourite\s"[/this\s((song|video)\s)?is/]

=> "this song is"

irb(main):102:0> "this flower is my favourite\s"[/this\s((song|video)\s)?is/]

=> nil

irb(main):103:0> "this video is my favourite\s"[/this\s((song|video)\s)?is/]

=> "this video is"



irb(main):105:0> "anything you say"[/.*/]

=> "anything you say"

irb(main):119:0> "will be repeated"[/.*/]

=> "will be repeated"

irb(main):116:0> "good times"[/.*[^<\/p>]/]

=> "good times"



irb(main):220:0> "test 123 test 123"[/\d+/]

=> "123"

irb(main):224:0> "test 123 test 123"[/\d{2}/]

=> "12"

irb(main):226:0> "test 123 test 123"[/\w+/]

=> "test"



irb(main):008:0> "try this test that"[/try.\b\w+/]

=> "try this"

irb(main):009:0> "try this test that"[/test.\b\w+/]

=> "test that"



irb(main):233:0> "test 123 test 123"[/\w+\s\d+/]

=> "test 123"

irb(main):248:0> "test 123 test 123"[/\w+\s\d+.*/]

=> "test 123 test 123"

irb(main):249:0> "test this test 123"[/\w+\s\d+.*/]

=> "test 123"

irb(main):250:0> "test this test that"[/\w+\s\d+.*/]

=> nil

irb(main):279:0> "try this test that"[/try\s\w[^\s]+/]

=> "try this"

irb(main):280:0> "try this test that"[/test\s\w[^\s]+/]

=> "test that"



irb(main):310:0> "try this test that"[/test\s\w\B+/]

=> "test tha"

irb(main):308:0> "try this test that"[/try\s\w\B+./]

=> "try this"

irb(main):309:0> "try this test that"[/test\s\w\B+./]

=> "test that"



irb(main):322:0> "try this test that"[/try\s\w+\b/]

=> "try this"

irb(main):323:0> "try this test that"[/test\s\w+\b/]

=> "test that"



irb(main):008:0> "try this test that"[/try.\b\w+/]

=> "try this"

irb(main):009:0> "try this test that"[/test.\b\w+/]

=> "test that"



irb(main):010:0> "try this test that"[/test.\w+/]

=> "test that"

irb(main):011:0> "try this test that"[/try.\w+/]

=> "try this"



irb(main):012:0> "try this test that"[/try\s\w+/]

=> "try this"

irb(main):013:0> "try this test that"[/test\s\w+/]

=> "test that"



irb(main):015:0> "try this test that"[/try\s\w+\s\w+/]

=> "try this test"



irb(main):041:0> "try this test that"[/\w+\s\w+$/]

=> "test that"

irb(main):043:0> "try this test that"[/^\w+\s\w+/]

=> "try this"

Note: Similar to CSS the more specific an expression or selector is the less ambiguous it is.

Calendar Loops

jcongote (John Edgar Congote Calle) — Fri, 22 Sep 2006 20:13:23 GMT

this program is very usefull when you need to know the list of dates of a repetitive task in the week.

I create this program to fill the records of my teaches in a school.



#include 





int meses[12]={31,28,31,30,31,30,31,31,30,31,30,31};

int dias[365][3];

/*

0 Lunes

1 Martes

2 Miercoles

3 Jueves

4 Viernes

5 Sabado

6 Domingo

*/



int cursos[7][4]={{0,0,0,0},{2,2,0,0},{1,0,1,1},{0,1,0,0},{0,0,2,2},{0,0,0,0},{0,0,0,0}};



int main(){

    int i,j,k;

    dias[0][0]=5;

    for (i=1;i<365;i++){

        dias[i][0]=(dias[i-1][0]+1)%7;                       

    }    

    k=0;

    for (i=0;i<12;i++){

        for (j=1;j<=meses[i];j++){

            dias[k][1]=i;    

            dias[k][2]=j;

            k++;

        }

    }

    

    for (i=0;i<365;i++){

       // bool salto=false;

        for (j=0;j<4;j++){



            for (k=0;k                printf("6-%c \t %i - %i \n",'A'+j,dias[i][2]+1,dias[i][1]+1);

//                salto=true;

            }               

        }    

       // if (salto)

       //    printf("\n");

    }

    

    return 0;

}

DZone Snippets: repetition code

Repetition in Regular Expressions

Calendar Loops