Using DeleteCases to match a string pattern

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I am trying to remove all of the elements from a list that contain the characters "err" in that order.



I expect the following code to return an empty list:



DeleteCases["Aerr", __ ~~ "err"]


However it fails to recognize the pattern and will return the full List. What am I missing in the documentation for patterns? Perhaps it is an issue with DeleteCases, as I can use StringMatchQ to identify that the patterns match.



StringMatchQ["Aerr", __ ~~ "err"]


Returns True.






pattern-matching filtering







share|improve this question









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Karl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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    up vote
    2
    down vote

    favorite












    I am trying to remove all of the elements from a list that contain the characters "err" in that order.



    I expect the following code to return an empty list:



    DeleteCases["Aerr", __ ~~ "err"]


    However it fails to recognize the pattern and will return the full List. What am I missing in the documentation for patterns? Perhaps it is an issue with DeleteCases, as I can use StringMatchQ to identify that the patterns match.



    StringMatchQ["Aerr", __ ~~ "err"]


    Returns True.






    pattern-matching filtering







    share|improve this question









    New contributor




    Karl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.





















      up vote
      2
      down vote

      favorite









      up vote
      2
      down vote

      favorite











      I am trying to remove all of the elements from a list that contain the characters "err" in that order.



      I expect the following code to return an empty list:



      DeleteCases["Aerr", __ ~~ "err"]


      However it fails to recognize the pattern and will return the full List. What am I missing in the documentation for patterns? Perhaps it is an issue with DeleteCases, as I can use StringMatchQ to identify that the patterns match.



      StringMatchQ["Aerr", __ ~~ "err"]


      Returns True.






      pattern-matching filtering







      share|improve this question









      New contributor




      Karl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      I am trying to remove all of the elements from a list that contain the characters "err" in that order.



      I expect the following code to return an empty list:



      DeleteCases["Aerr", __ ~~ "err"]


      However it fails to recognize the pattern and will return the full List. What am I missing in the documentation for patterns? Perhaps it is an issue with DeleteCases, as I can use StringMatchQ to identify that the patterns match.



      StringMatchQ["Aerr", __ ~~ "err"]


      Returns True.






      pattern-matching filtering




      pattern-matching filtering






      share|improve this question









      New contributor




      Karl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      share|improve this question









      New contributor




      Karl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      share|improve this question




      share|improve this question








      edited 14 mins ago









      Carl Woll

      63.2k282163




      63.2k282163






      New contributor




      Karl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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      asked 29 mins ago









      Karl

      113




      113




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      New contributor





      Karl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






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          2 Answers
          2






          active

          oldest

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          up vote
          2
          down vote













          First note the FullForm of your pattern:



          __ ~~ "err" //FullForm



          StringExpression[BlankSequence,"err"]




          The pattern is a StringExpression, so you must use a string function, e.g., StringMatchQ instead of DeleteCases, which is expecting a normal pattern. Here are some other possibilities:



          list = "Aerr";

          Select[list, Not @* StringMatchQ[__ ~~ "err"]]
          Pick[list, StringMatchQ[list, __ ~~ "err"], False]











          share|improve this answer



























            up vote
            1
            down vote













            DeleteCases["Aerr", _?(StringMatchQ[ "*err"]) ]






            For versions prior to version 10:



            DeleteCases["Aerr", _?(StringMatchQ[#, "*err"] &)]









            share|improve this answer






















            • While I appreciate the working example, I would have loved further explanation of how it works. I've gathered that the "?" syntax is a pattern test, but how does the "_" pattern which is for a single character match "Aerr"? Also, is it a bug that the code in my original question didn't work, or a misunderstanding of how to use patterns?
              – Karl
              9 mins ago










            • @Karl, please see Carl' Woll's answer for a detailed explanation.
              – kglr
              5 mins ago










            Your Answer





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            2 Answers
            2






            active

            oldest

            votes








            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            2
            down vote













            First note the FullForm of your pattern:



            __ ~~ "err" //FullForm



            StringExpression[BlankSequence,"err"]




            The pattern is a StringExpression, so you must use a string function, e.g., StringMatchQ instead of DeleteCases, which is expecting a normal pattern. Here are some other possibilities:



            list = "Aerr";

            Select[list, Not @* StringMatchQ[__ ~~ "err"]]
            Pick[list, StringMatchQ[list, __ ~~ "err"], False]











            share|improve this answer
























              up vote
              2
              down vote













              First note the FullForm of your pattern:



              __ ~~ "err" //FullForm



              StringExpression[BlankSequence,"err"]




              The pattern is a StringExpression, so you must use a string function, e.g., StringMatchQ instead of DeleteCases, which is expecting a normal pattern. Here are some other possibilities:



              list = "Aerr";

              Select[list, Not @* StringMatchQ[__ ~~ "err"]]
              Pick[list, StringMatchQ[list, __ ~~ "err"], False]











              share|improve this answer






















                up vote
                2
                down vote










                up vote
                2
                down vote









                First note the FullForm of your pattern:



                __ ~~ "err" //FullForm



                StringExpression[BlankSequence,"err"]




                The pattern is a StringExpression, so you must use a string function, e.g., StringMatchQ instead of DeleteCases, which is expecting a normal pattern. Here are some other possibilities:



                list = "Aerr";

                Select[list, Not @* StringMatchQ[__ ~~ "err"]]
                Pick[list, StringMatchQ[list, __ ~~ "err"], False]











                share|improve this answer












                First note the FullForm of your pattern:



                __ ~~ "err" //FullForm



                StringExpression[BlankSequence,"err"]




                The pattern is a StringExpression, so you must use a string function, e.g., StringMatchQ instead of DeleteCases, which is expecting a normal pattern. Here are some other possibilities:



                list = "Aerr";

                Select[list, Not @* StringMatchQ[__ ~~ "err"]]
                Pick[list, StringMatchQ[list, __ ~~ "err"], False]












                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered 10 mins ago









                Carl Woll

                63.2k282163




                63.2k282163




















                    up vote
                    1
                    down vote













                    DeleteCases["Aerr", _?(StringMatchQ[ "*err"]) ]






                    For versions prior to version 10:



                    DeleteCases["Aerr", _?(StringMatchQ[#, "*err"] &)]









                    share|improve this answer






















                    • While I appreciate the working example, I would have loved further explanation of how it works. I've gathered that the "?" syntax is a pattern test, but how does the "_" pattern which is for a single character match "Aerr"? Also, is it a bug that the code in my original question didn't work, or a misunderstanding of how to use patterns?
                      – Karl
                      9 mins ago










                    • @Karl, please see Carl' Woll's answer for a detailed explanation.
                      – kglr
                      5 mins ago














                    up vote
                    1
                    down vote













                    DeleteCases["Aerr", _?(StringMatchQ[ "*err"]) ]






                    For versions prior to version 10:



                    DeleteCases["Aerr", _?(StringMatchQ[#, "*err"] &)]









                    share|improve this answer






















                    • While I appreciate the working example, I would have loved further explanation of how it works. I've gathered that the "?" syntax is a pattern test, but how does the "_" pattern which is for a single character match "Aerr"? Also, is it a bug that the code in my original question didn't work, or a misunderstanding of how to use patterns?
                      – Karl
                      9 mins ago










                    • @Karl, please see Carl' Woll's answer for a detailed explanation.
                      – kglr
                      5 mins ago












                    up vote
                    1
                    down vote










                    up vote
                    1
                    down vote









                    DeleteCases["Aerr", _?(StringMatchQ[ "*err"]) ]






                    For versions prior to version 10:



                    DeleteCases["Aerr", _?(StringMatchQ[#, "*err"] &)]









                    share|improve this answer














                    DeleteCases["Aerr", _?(StringMatchQ[ "*err"]) ]






                    For versions prior to version 10:



                    DeleteCases["Aerr", _?(StringMatchQ[#, "*err"] &)]










                    share|improve this answer














                    share|improve this answer



                    share|improve this answer








                    edited 12 mins ago

























                    answered 25 mins ago









                    kglr

                    168k8192395




                    168k8192395











                    • While I appreciate the working example, I would have loved further explanation of how it works. I've gathered that the "?" syntax is a pattern test, but how does the "_" pattern which is for a single character match "Aerr"? Also, is it a bug that the code in my original question didn't work, or a misunderstanding of how to use patterns?
                      – Karl
                      9 mins ago










                    • @Karl, please see Carl' Woll's answer for a detailed explanation.
                      – kglr
                      5 mins ago
















                    • While I appreciate the working example, I would have loved further explanation of how it works. I've gathered that the "?" syntax is a pattern test, but how does the "_" pattern which is for a single character match "Aerr"? Also, is it a bug that the code in my original question didn't work, or a misunderstanding of how to use patterns?
                      – Karl
                      9 mins ago










                    • @Karl, please see Carl' Woll's answer for a detailed explanation.
                      – kglr
                      5 mins ago















                    While I appreciate the working example, I would have loved further explanation of how it works. I've gathered that the "?" syntax is a pattern test, but how does the "_" pattern which is for a single character match "Aerr"? Also, is it a bug that the code in my original question didn't work, or a misunderstanding of how to use patterns?
                    – Karl
                    9 mins ago




                    While I appreciate the working example, I would have loved further explanation of how it works. I've gathered that the "?" syntax is a pattern test, but how does the "_" pattern which is for a single character match "Aerr"? Also, is it a bug that the code in my original question didn't work, or a misunderstanding of how to use patterns?
                    – Karl
                    9 mins ago












                    @Karl, please see Carl' Woll's answer for a detailed explanation.
                    – kglr
                    5 mins ago




                    @Karl, please see Carl' Woll's answer for a detailed explanation.
                    – kglr
                    5 mins ago










                    Karl is a new contributor. Be nice, and check out our Code of Conduct.









                     

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