What are the performance advantage of Elixir's defstruct?











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My understanding of Elixir's structure is that;

1. It can't hold keys other than ones defined at compile time.

2. It can have default values, which is evaluated at compile time.



Is there are any performance advantage?

Also, is there anything that I'm missing?










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  • 1




    From the docs: "Structs can also be used in pattern matching, both for matching on the value of specific keys as well as for ensuring that the matching value is a struct of the same type as the matched value." So you can win by pattern matching rather than using less performant algorithmic method - I guess.
    – GavinBrelstaff
    Nov 14 at 7:52

















up vote
0
down vote

favorite












My understanding of Elixir's structure is that;

1. It can't hold keys other than ones defined at compile time.

2. It can have default values, which is evaluated at compile time.



Is there are any performance advantage?

Also, is there anything that I'm missing?










share|improve this question


















  • 1




    From the docs: "Structs can also be used in pattern matching, both for matching on the value of specific keys as well as for ensuring that the matching value is a struct of the same type as the matched value." So you can win by pattern matching rather than using less performant algorithmic method - I guess.
    – GavinBrelstaff
    Nov 14 at 7:52















up vote
0
down vote

favorite









up vote
0
down vote

favorite











My understanding of Elixir's structure is that;

1. It can't hold keys other than ones defined at compile time.

2. It can have default values, which is evaluated at compile time.



Is there are any performance advantage?

Also, is there anything that I'm missing?










share|improve this question













My understanding of Elixir's structure is that;

1. It can't hold keys other than ones defined at compile time.

2. It can have default values, which is evaluated at compile time.



Is there are any performance advantage?

Also, is there anything that I'm missing?







elixir structure






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asked Nov 14 at 6:02









HelloWorld

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7416








  • 1




    From the docs: "Structs can also be used in pattern matching, both for matching on the value of specific keys as well as for ensuring that the matching value is a struct of the same type as the matched value." So you can win by pattern matching rather than using less performant algorithmic method - I guess.
    – GavinBrelstaff
    Nov 14 at 7:52
















  • 1




    From the docs: "Structs can also be used in pattern matching, both for matching on the value of specific keys as well as for ensuring that the matching value is a struct of the same type as the matched value." So you can win by pattern matching rather than using less performant algorithmic method - I guess.
    – GavinBrelstaff
    Nov 14 at 7:52










1




1




From the docs: "Structs can also be used in pattern matching, both for matching on the value of specific keys as well as for ensuring that the matching value is a struct of the same type as the matched value." So you can win by pattern matching rather than using less performant algorithmic method - I guess.
– GavinBrelstaff
Nov 14 at 7:52






From the docs: "Structs can also be used in pattern matching, both for matching on the value of specific keys as well as for ensuring that the matching value is a struct of the same type as the matched value." So you can win by pattern matching rather than using less performant algorithmic method - I guess.
– GavinBrelstaff
Nov 14 at 7:52














2 Answers
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The main advantage of struct is not any performance, but code readability and correctness. Consider something like %{id: 123} - we don't know what that map represents. With structs we can have %Person{id: 123} and %Company{id: 123}, and these will be different things. Furthermore one can easily express which one is expected with pattern matching, as mentioned by GavinBrelstaff. Another example of a feature in struct aimed at correctness is @enforce_keys - by setting it in your struct you make sure that any normally created instance of it will have the given keys present.






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    Well, Elixir is open source. As it might be easily seen from the implementation of Kernel.defstruct/1, everything it does is it defines __struct__ method on the module where it was called (only the false part of the case could be considered without the loss of generality).



    Everything else there is responsible for informing the Elixir compiler about this struct to enable new syntax (%MyStruct{}) for it and to store some metainformation about the struct into compiler globals.



    Underneath the struct is represented by bare map %{} and there could not be any room for any performance boost.






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      2 Answers
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      accepted










      The main advantage of struct is not any performance, but code readability and correctness. Consider something like %{id: 123} - we don't know what that map represents. With structs we can have %Person{id: 123} and %Company{id: 123}, and these will be different things. Furthermore one can easily express which one is expected with pattern matching, as mentioned by GavinBrelstaff. Another example of a feature in struct aimed at correctness is @enforce_keys - by setting it in your struct you make sure that any normally created instance of it will have the given keys present.






      share|improve this answer

























        up vote
        2
        down vote



        accepted










        The main advantage of struct is not any performance, but code readability and correctness. Consider something like %{id: 123} - we don't know what that map represents. With structs we can have %Person{id: 123} and %Company{id: 123}, and these will be different things. Furthermore one can easily express which one is expected with pattern matching, as mentioned by GavinBrelstaff. Another example of a feature in struct aimed at correctness is @enforce_keys - by setting it in your struct you make sure that any normally created instance of it will have the given keys present.






        share|improve this answer























          up vote
          2
          down vote



          accepted







          up vote
          2
          down vote



          accepted






          The main advantage of struct is not any performance, but code readability and correctness. Consider something like %{id: 123} - we don't know what that map represents. With structs we can have %Person{id: 123} and %Company{id: 123}, and these will be different things. Furthermore one can easily express which one is expected with pattern matching, as mentioned by GavinBrelstaff. Another example of a feature in struct aimed at correctness is @enforce_keys - by setting it in your struct you make sure that any normally created instance of it will have the given keys present.






          share|improve this answer












          The main advantage of struct is not any performance, but code readability and correctness. Consider something like %{id: 123} - we don't know what that map represents. With structs we can have %Person{id: 123} and %Company{id: 123}, and these will be different things. Furthermore one can easily express which one is expected with pattern matching, as mentioned by GavinBrelstaff. Another example of a feature in struct aimed at correctness is @enforce_keys - by setting it in your struct you make sure that any normally created instance of it will have the given keys present.







          share|improve this answer












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          answered Nov 14 at 14:06









          Paweł Obrok

          17.2k56060




          17.2k56060
























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              Well, Elixir is open source. As it might be easily seen from the implementation of Kernel.defstruct/1, everything it does is it defines __struct__ method on the module where it was called (only the false part of the case could be considered without the loss of generality).



              Everything else there is responsible for informing the Elixir compiler about this struct to enable new syntax (%MyStruct{}) for it and to store some metainformation about the struct into compiler globals.



              Underneath the struct is represented by bare map %{} and there could not be any room for any performance boost.






              share|improve this answer

























                up vote
                1
                down vote













                Well, Elixir is open source. As it might be easily seen from the implementation of Kernel.defstruct/1, everything it does is it defines __struct__ method on the module where it was called (only the false part of the case could be considered without the loss of generality).



                Everything else there is responsible for informing the Elixir compiler about this struct to enable new syntax (%MyStruct{}) for it and to store some metainformation about the struct into compiler globals.



                Underneath the struct is represented by bare map %{} and there could not be any room for any performance boost.






                share|improve this answer























                  up vote
                  1
                  down vote










                  up vote
                  1
                  down vote









                  Well, Elixir is open source. As it might be easily seen from the implementation of Kernel.defstruct/1, everything it does is it defines __struct__ method on the module where it was called (only the false part of the case could be considered without the loss of generality).



                  Everything else there is responsible for informing the Elixir compiler about this struct to enable new syntax (%MyStruct{}) for it and to store some metainformation about the struct into compiler globals.



                  Underneath the struct is represented by bare map %{} and there could not be any room for any performance boost.






                  share|improve this answer












                  Well, Elixir is open source. As it might be easily seen from the implementation of Kernel.defstruct/1, everything it does is it defines __struct__ method on the module where it was called (only the false part of the case could be considered without the loss of generality).



                  Everything else there is responsible for informing the Elixir compiler about this struct to enable new syntax (%MyStruct{}) for it and to store some metainformation about the struct into compiler globals.



                  Underneath the struct is represented by bare map %{} and there could not be any room for any performance boost.







                  share|improve this answer












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                  answered Nov 14 at 13:48









                  Aleksei Matiushkin

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                  77.3k95088






























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