Pure functions as a replacement of constant mappings?












2














I need to create a lookup table [uint -> uint] that is constant.



Constant mappings or switch-case are not available in solidity. Are pure functions full of if-else the only option?



Any better suggestion?






solidity mapping pure







share|improve this question






















  • It seems from discussion below that this question is about gas optimization.
    – smarx
    1 hour ago
















2














I need to create a lookup table [uint -> uint] that is constant.



Constant mappings or switch-case are not available in solidity. Are pure functions full of if-else the only option?



Any better suggestion?






solidity mapping pure







share|improve this question






















  • It seems from discussion below that this question is about gas optimization.
    – smarx
    1 hour ago














2












2








2


1





I need to create a lookup table [uint -> uint] that is constant.



Constant mappings or switch-case are not available in solidity. Are pure functions full of if-else the only option?



Any better suggestion?






solidity mapping pure







share|improve this question













I need to create a lookup table [uint -> uint] that is constant.



Constant mappings or switch-case are not available in solidity. Are pure functions full of if-else the only option?



Any better suggestion?






solidity mapping pure




solidity mapping pure






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked 4 hours ago









purpletentacle

1163




1163












  • It seems from discussion below that this question is about gas optimization.
    – smarx
    1 hour ago


















  • It seems from discussion below that this question is about gas optimization.
    – smarx
    1 hour ago
















It seems from discussion below that this question is about gas optimization.
– smarx
1 hour ago




It seems from discussion below that this question is about gas optimization.
– smarx
1 hour ago










2 Answers
2






active

oldest

votes


















2














I don't see a dilemma.



You can have a mapping:



mapping(uint => uint) public myMap;


You can populate some locations in the constructor or elsewhere:



constructor() public {

  myMap[1] = 101;

  myMap[2] = 201;

}


That gives you a simple view function (myMap(uint) public view returns(uint)) that returns the number stored at an index.



You can also make view functions full of if/else if that's the best approach for your use-case.



Elaborate on the question with some hints about what you want to accomplish and possibly more specific guidance will be possible.



Hope it helps.






share|improve this answer





















  • Well, clearly I want to minimize gas. What do you think would be more efficient?
    – purpletentacle
    2 hours ago



















0














The else-if function is by far less efficient that mapping in case of sparse data if there are not special criteria for searching.



If, on the contrary, you fill all the holes in the range of interest, a simple array is the best solution.






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









    2














    I don't see a dilemma.



    You can have a mapping:



    mapping(uint => uint) public myMap;


    You can populate some locations in the constructor or elsewhere:



    constructor() public {
    
  myMap[1] = 101;
    
  myMap[2] = 201;
    
}


    That gives you a simple view function (myMap(uint) public view returns(uint)) that returns the number stored at an index.



    You can also make view functions full of if/else if that's the best approach for your use-case.



    Elaborate on the question with some hints about what you want to accomplish and possibly more specific guidance will be possible.



    Hope it helps.






    share|improve this answer





















    • Well, clearly I want to minimize gas. What do you think would be more efficient?
      – purpletentacle
      2 hours ago
















    2














    I don't see a dilemma.



    You can have a mapping:



    mapping(uint => uint) public myMap;


    You can populate some locations in the constructor or elsewhere:



    constructor() public {
    
  myMap[1] = 101;
    
  myMap[2] = 201;
    
}


    That gives you a simple view function (myMap(uint) public view returns(uint)) that returns the number stored at an index.



    You can also make view functions full of if/else if that's the best approach for your use-case.



    Elaborate on the question with some hints about what you want to accomplish and possibly more specific guidance will be possible.



    Hope it helps.






    share|improve this answer





















    • Well, clearly I want to minimize gas. What do you think would be more efficient?
      – purpletentacle
      2 hours ago














    2












    2








    2






    I don't see a dilemma.



    You can have a mapping:



    mapping(uint => uint) public myMap;


    You can populate some locations in the constructor or elsewhere:



    constructor() public {
    
  myMap[1] = 101;
    
  myMap[2] = 201;
    
}


    That gives you a simple view function (myMap(uint) public view returns(uint)) that returns the number stored at an index.



    You can also make view functions full of if/else if that's the best approach for your use-case.



    Elaborate on the question with some hints about what you want to accomplish and possibly more specific guidance will be possible.



    Hope it helps.






    share|improve this answer












    I don't see a dilemma.



    You can have a mapping:



    mapping(uint => uint) public myMap;


    You can populate some locations in the constructor or elsewhere:



    constructor() public {
    
  myMap[1] = 101;
    
  myMap[2] = 201;
    
}


    That gives you a simple view function (myMap(uint) public view returns(uint)) that returns the number stored at an index.



    You can also make view functions full of if/else if that's the best approach for your use-case.



    Elaborate on the question with some hints about what you want to accomplish and possibly more specific guidance will be possible.



    Hope it helps.







    share|improve this answer












    share|improve this answer



    share|improve this answer










    answered 4 hours ago









    Rob Hitchens B9lab

    25.9k54278




    25.9k54278












    • Well, clearly I want to minimize gas. What do you think would be more efficient?
      – purpletentacle
      2 hours ago


















    • Well, clearly I want to minimize gas. What do you think would be more efficient?
      – purpletentacle
      2 hours ago
















    Well, clearly I want to minimize gas. What do you think would be more efficient?
    – purpletentacle
    2 hours ago




    Well, clearly I want to minimize gas. What do you think would be more efficient?
    – purpletentacle
    2 hours ago











    0














    The else-if function is by far less efficient that mapping in case of sparse data if there are not special criteria for searching.



    If, on the contrary, you fill all the holes in the range of interest, a simple array is the best solution.






    share|improve this answer


























      0














      The else-if function is by far less efficient that mapping in case of sparse data if there are not special criteria for searching.



      If, on the contrary, you fill all the holes in the range of interest, a simple array is the best solution.






      share|improve this answer
























        0












        0








        0






        The else-if function is by far less efficient that mapping in case of sparse data if there are not special criteria for searching.



        If, on the contrary, you fill all the holes in the range of interest, a simple array is the best solution.






        share|improve this answer












        The else-if function is by far less efficient that mapping in case of sparse data if there are not special criteria for searching.



        If, on the contrary, you fill all the holes in the range of interest, a simple array is the best solution.







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered 1 hour ago









        Rick Park

        778111




        778111






























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