Perl6 getting a regex from a string





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I want to put a regex in a YAML config file (say: config/filename.yaml), eg.



-
section: Begining
regex: '/ ^ <[ a..b, A..B ]> /'
-
section: Next
regex: '/ ^ <[ c..z, C..Z ]> /'


When I read this into a hash (eg. using YAMLish), eg.,



use YAMLish;
my @h = load-yaml('config/filename.yaml'.IO.slurp);


naturally I have a string in @h[0]<regex>



So how do I recover a regex from a string for use in a match?



I want something like the following, but the following doesn't work:



say 'Its a beginning' if 'A beginning' ~~ @h[0]<regex>


It doesn't work as desired because @h[0]<regex> is a Str, so the smart match is testing a Str in @h[0]<regex> against a Str literal. So how to get the regex out of the Str?










share|improve this question





























    8















    I want to put a regex in a YAML config file (say: config/filename.yaml), eg.



    -
    section: Begining
    regex: '/ ^ <[ a..b, A..B ]> /'
    -
    section: Next
    regex: '/ ^ <[ c..z, C..Z ]> /'


    When I read this into a hash (eg. using YAMLish), eg.,



    use YAMLish;
    my @h = load-yaml('config/filename.yaml'.IO.slurp);


    naturally I have a string in @h[0]<regex>



    So how do I recover a regex from a string for use in a match?



    I want something like the following, but the following doesn't work:



    say 'Its a beginning' if 'A beginning' ~~ @h[0]<regex>


    It doesn't work as desired because @h[0]<regex> is a Str, so the smart match is testing a Str in @h[0]<regex> against a Str literal. So how to get the regex out of the Str?










    share|improve this question

























      8












      8








      8


      1






      I want to put a regex in a YAML config file (say: config/filename.yaml), eg.



      -
      section: Begining
      regex: '/ ^ <[ a..b, A..B ]> /'
      -
      section: Next
      regex: '/ ^ <[ c..z, C..Z ]> /'


      When I read this into a hash (eg. using YAMLish), eg.,



      use YAMLish;
      my @h = load-yaml('config/filename.yaml'.IO.slurp);


      naturally I have a string in @h[0]<regex>



      So how do I recover a regex from a string for use in a match?



      I want something like the following, but the following doesn't work:



      say 'Its a beginning' if 'A beginning' ~~ @h[0]<regex>


      It doesn't work as desired because @h[0]<regex> is a Str, so the smart match is testing a Str in @h[0]<regex> against a Str literal. So how to get the regex out of the Str?










      share|improve this question














      I want to put a regex in a YAML config file (say: config/filename.yaml), eg.



      -
      section: Begining
      regex: '/ ^ <[ a..b, A..B ]> /'
      -
      section: Next
      regex: '/ ^ <[ c..z, C..Z ]> /'


      When I read this into a hash (eg. using YAMLish), eg.,



      use YAMLish;
      my @h = load-yaml('config/filename.yaml'.IO.slurp);


      naturally I have a string in @h[0]<regex>



      So how do I recover a regex from a string for use in a match?



      I want something like the following, but the following doesn't work:



      say 'Its a beginning' if 'A beginning' ~~ @h[0]<regex>


      It doesn't work as desired because @h[0]<regex> is a Str, so the smart match is testing a Str in @h[0]<regex> against a Str literal. So how to get the regex out of the Str?







      regex perl6






      share|improve this question













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      asked Nov 24 '18 at 14:44









      Richard HainsworthRichard Hainsworth

      22216




      22216
























          2 Answers
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          11














          You interpolate a string held in a variable $var into a regex via / <$var> /, or, in case of more complex expressions like yours, / <{ @h[0]<regex> }> /.



          Note, however, that you first have to remove the enclosing slashes from your string. For trusted input, there's of course always EVAL...






          share|improve this answer































            1














            I think it's a good idea to compile external regexes, so you know right away if they fail (and they will be faster afterwards):



            Perl6 REPL:



            > my $str = 'd+'; my $rx = rx/ <$str> /; say "a" ~~ $rx; say "10" ~~ $rx
            Nil
            「10」


            Of course it's easier providing a "pure" regex, not one that also has syntax (/ /).



            Perl documentation






            share|improve this answer


























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              2 Answers
              2






              active

              oldest

              votes








              2 Answers
              2






              active

              oldest

              votes









              active

              oldest

              votes






              active

              oldest

              votes









              11














              You interpolate a string held in a variable $var into a regex via / <$var> /, or, in case of more complex expressions like yours, / <{ @h[0]<regex> }> /.



              Note, however, that you first have to remove the enclosing slashes from your string. For trusted input, there's of course always EVAL...






              share|improve this answer




























                11














                You interpolate a string held in a variable $var into a regex via / <$var> /, or, in case of more complex expressions like yours, / <{ @h[0]<regex> }> /.



                Note, however, that you first have to remove the enclosing slashes from your string. For trusted input, there's of course always EVAL...






                share|improve this answer


























                  11












                  11








                  11







                  You interpolate a string held in a variable $var into a regex via / <$var> /, or, in case of more complex expressions like yours, / <{ @h[0]<regex> }> /.



                  Note, however, that you first have to remove the enclosing slashes from your string. For trusted input, there's of course always EVAL...






                  share|improve this answer













                  You interpolate a string held in a variable $var into a regex via / <$var> /, or, in case of more complex expressions like yours, / <{ @h[0]<regex> }> /.



                  Note, however, that you first have to remove the enclosing slashes from your string. For trusted input, there's of course always EVAL...







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered Nov 24 '18 at 14:52









                  ChristophChristoph

                  131k32161219




                  131k32161219

























                      1














                      I think it's a good idea to compile external regexes, so you know right away if they fail (and they will be faster afterwards):



                      Perl6 REPL:



                      > my $str = 'd+'; my $rx = rx/ <$str> /; say "a" ~~ $rx; say "10" ~~ $rx
                      Nil
                      「10」


                      Of course it's easier providing a "pure" regex, not one that also has syntax (/ /).



                      Perl documentation






                      share|improve this answer






























                        1














                        I think it's a good idea to compile external regexes, so you know right away if they fail (and they will be faster afterwards):



                        Perl6 REPL:



                        > my $str = 'd+'; my $rx = rx/ <$str> /; say "a" ~~ $rx; say "10" ~~ $rx
                        Nil
                        「10」


                        Of course it's easier providing a "pure" regex, not one that also has syntax (/ /).



                        Perl documentation






                        share|improve this answer




























                          1












                          1








                          1







                          I think it's a good idea to compile external regexes, so you know right away if they fail (and they will be faster afterwards):



                          Perl6 REPL:



                          > my $str = 'd+'; my $rx = rx/ <$str> /; say "a" ~~ $rx; say "10" ~~ $rx
                          Nil
                          「10」


                          Of course it's easier providing a "pure" regex, not one that also has syntax (/ /).



                          Perl documentation






                          share|improve this answer















                          I think it's a good idea to compile external regexes, so you know right away if they fail (and they will be faster afterwards):



                          Perl6 REPL:



                          > my $str = 'd+'; my $rx = rx/ <$str> /; say "a" ~~ $rx; say "10" ~~ $rx
                          Nil
                          「10」


                          Of course it's easier providing a "pure" regex, not one that also has syntax (/ /).



                          Perl documentation







                          share|improve this answer














                          share|improve this answer



                          share|improve this answer








                          edited Dec 9 '18 at 11:46

























                          answered Dec 9 '18 at 11:38









                          nxadmnxadm

                          1,9711016




                          1,9711016






























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