F # Types and Function Signatures

Question

I am new to F # and I am trying something to plunge into the language.

I have two types, almost identical (Coordinates and Vector). Due to this type, the output may not work properly, and it is difficult for me to determine the correct type for each function.

It is somehow unknown that Vector is here:

type Coordinate = {X:int; Y:int}
type Vector = {X:int; Y:int}

let calculateVector (origin:Coordinate) (destination:Coordinate) = { X=destination.X-origin.X; Y= destination.Y-origin.Y;}

And so, when I need a return type of type Coordinate, I can’t find how to specify it for this function:

let calculateNextCoordinate (coordinate:Coordinate) direction = 
   match direction with
   | "N" -> { X=coordinate.X; Y=coordinate.Y-1 }
   | "NE" -> { X=coordinate.X+1; Y=coordinate.Y-1 }
   | "E" -> { X=coordinate.X+1; Y=coordinate.Y }
   | "SE" -> { X=coordinate.X+1; Y=coordinate.Y+1 }
   | "S" -> { X=coordinate.X; Y=coordinate.Y+1 }
   | "SW" -> { X=coordinate.X-1; Y=coordinate.Y+1 }
   | "W" -> { X=coordinate.X-1; Y=coordinate.Y }
   | "NW" -> { X=coordinate.X-1; Y=coordinate.Y-1 }
   | _ -> coordinate

I have this error in the default case: this expression should have had a "Vector", but there is a type of "Coordinate"

I'm tired of looking at this site for feature signatures, but could not get something for my problem: https://fsharpforfunandprofit.com/posts/function-signatures/

Questions:

How do you fix this error?

, , ( Vector)?

: F #?

Answer 1

:

{ X = 2; Y = 3}

Vector Coordinate. F # , {X =..., Y =...} .

F # records fsharpforfunandprofit.com, , , .

, , :

{ Coordinate.X = 2; Y = 3 }  // Creates a Coordinate
{ X = 2; Coordinate.Y = 3 }  // Creates a Coordinate

{ Vector.X = 2; Y = 3 } // creates a vector