How to fix “pattern-matching is not exhaustive”,












0















I want to write function that will add two elements of type eval



type eval = Num of float | Neg | Add | Sub | Mul | Div;;


OCaml compiler gives me this warning, but I do not know exactly what it wants. It works, but I want to make it without this warning.



# let (+++) (Num a) (Num b) =

  match (Num a), (Num b) with

  | (Add|Neg|Sub|Mul|Div), _ -> failwith "01"

  | _, (Add|Neg|Sub|Mul|Div) -> failwith "02"

  | _, _ -> Num (a +. b)

  ;;        

Warning 8: this pattern-matching is not exhaustive.

Here is an example of a case that is not matched:

(Neg|Add|Sub|Mul|Div)

Warning 8: this pattern-matching is not exhaustive.

Here is an example of a case that is not matched:

(Neg|Add|Sub|Mul|Div)

val ( +++ ) : eval -> eval -> eval = <fun>





function functional-programming ocaml







share|improve this question




















  • 1





    Try calling your +++ function with anything other than a Num. Your failwith "01" and failwith "02" cases will never be reached.

    – sepp2k
    Nov 28 '18 at 14:29
















0















I want to write function that will add two elements of type eval



type eval = Num of float | Neg | Add | Sub | Mul | Div;;


OCaml compiler gives me this warning, but I do not know exactly what it wants. It works, but I want to make it without this warning.



# let (+++) (Num a) (Num b) =

  match (Num a), (Num b) with

  | (Add|Neg|Sub|Mul|Div), _ -> failwith "01"

  | _, (Add|Neg|Sub|Mul|Div) -> failwith "02"

  | _, _ -> Num (a +. b)

  ;;        

Warning 8: this pattern-matching is not exhaustive.

Here is an example of a case that is not matched:

(Neg|Add|Sub|Mul|Div)

Warning 8: this pattern-matching is not exhaustive.

Here is an example of a case that is not matched:

(Neg|Add|Sub|Mul|Div)

val ( +++ ) : eval -> eval -> eval = <fun>





function functional-programming ocaml







share|improve this question




















  • 1





    Try calling your +++ function with anything other than a Num. Your failwith "01" and failwith "02" cases will never be reached.

    – sepp2k
    Nov 28 '18 at 14:29














0












0








0








I want to write function that will add two elements of type eval



type eval = Num of float | Neg | Add | Sub | Mul | Div;;


OCaml compiler gives me this warning, but I do not know exactly what it wants. It works, but I want to make it without this warning.



# let (+++) (Num a) (Num b) =

  match (Num a), (Num b) with

  | (Add|Neg|Sub|Mul|Div), _ -> failwith "01"

  | _, (Add|Neg|Sub|Mul|Div) -> failwith "02"

  | _, _ -> Num (a +. b)

  ;;        

Warning 8: this pattern-matching is not exhaustive.

Here is an example of a case that is not matched:

(Neg|Add|Sub|Mul|Div)

Warning 8: this pattern-matching is not exhaustive.

Here is an example of a case that is not matched:

(Neg|Add|Sub|Mul|Div)

val ( +++ ) : eval -> eval -> eval = <fun>





function functional-programming ocaml







share|improve this question
















I want to write function that will add two elements of type eval



type eval = Num of float | Neg | Add | Sub | Mul | Div;;


OCaml compiler gives me this warning, but I do not know exactly what it wants. It works, but I want to make it without this warning.



# let (+++) (Num a) (Num b) =

  match (Num a), (Num b) with

  | (Add|Neg|Sub|Mul|Div), _ -> failwith "01"

  | _, (Add|Neg|Sub|Mul|Div) -> failwith "02"

  | _, _ -> Num (a +. b)

  ;;        

Warning 8: this pattern-matching is not exhaustive.

Here is an example of a case that is not matched:

(Neg|Add|Sub|Mul|Div)

Warning 8: this pattern-matching is not exhaustive.

Here is an example of a case that is not matched:

(Neg|Add|Sub|Mul|Div)

val ( +++ ) : eval -> eval -> eval = <fun>





function functional-programming ocaml




function functional-programming ocaml






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 28 '18 at 21:29









rrauenza

3,53921835




3,53921835










asked Nov 28 '18 at 14:22









IlyaIlya

345




345








  • 1





    Try calling your +++ function with anything other than a Num. Your failwith "01" and failwith "02" cases will never be reached.

    – sepp2k
    Nov 28 '18 at 14:29














  • 1





    Try calling your +++ function with anything other than a Num. Your failwith "01" and failwith "02" cases will never be reached.

    – sepp2k
    Nov 28 '18 at 14:29








1




1





Try calling your +++ function with anything other than a Num. Your failwith "01" and failwith "02" cases will never be reached.

– sepp2k
Nov 28 '18 at 14:29





Try calling your +++ function with anything other than a Num. Your failwith "01" and failwith "02" cases will never be reached.

– sepp2k
Nov 28 '18 at 14:29












1 Answer
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The non-exhaustive patterns are here:



 let (+++) (Num a) (Num b) = ...


With those pattern, you are making the hypothesis that the argument of +++ are always of the form Num _ without enforcing it in the type system.
If you want to get rid of the warning you should expand the pattern matching to catch all other cases:



 let (+++) x y = match x, y with 

 | ...





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    1 Answer
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    1 Answer
    1






    active

    oldest

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    active

    oldest

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    active

    oldest

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    2














    The non-exhaustive patterns are here:



     let (+++) (Num a) (Num b) = ...


    With those pattern, you are making the hypothesis that the argument of +++ are always of the form Num _ without enforcing it in the type system.
    If you want to get rid of the warning you should expand the pattern matching to catch all other cases:



     let (+++) x y = match x, y with 
    
 | ...





    share|improve this answer




























      2














      The non-exhaustive patterns are here:



       let (+++) (Num a) (Num b) = ...


      With those pattern, you are making the hypothesis that the argument of +++ are always of the form Num _ without enforcing it in the type system.
      If you want to get rid of the warning you should expand the pattern matching to catch all other cases:



       let (+++) x y = match x, y with 
      
 | ...





      share|improve this answer


























        2












        2








        2







        The non-exhaustive patterns are here:



         let (+++) (Num a) (Num b) = ...


        With those pattern, you are making the hypothesis that the argument of +++ are always of the form Num _ without enforcing it in the type system.
        If you want to get rid of the warning you should expand the pattern matching to catch all other cases:



         let (+++) x y = match x, y with 
        
 | ...





        share|improve this answer













        The non-exhaustive patterns are here:



         let (+++) (Num a) (Num b) = ...


        With those pattern, you are making the hypothesis that the argument of +++ are always of the form Num _ without enforcing it in the type system.
        If you want to get rid of the warning you should expand the pattern matching to catch all other cases:



         let (+++) x y = match x, y with 
        
 | ...






        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 28 '18 at 14:29









        octachronoctachron

        5,2231614




        5,2231614
































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