Operators

Namespace: FsToolkit.ErrorHandling.Operator.ResultOption
FsToolkit.ErrorHandling provides the standard infix operators for the map (<!>), apply (<*>), and bind (>>=) functions of the Result<Option<_>,_> type.
In addition to these, it also offers an another infix operator <*^> for usage with normal Result values (without an inner Option). It has the following function signature:
Result<('a -> 'b) option, 'c> -> Result<'a, 'c> 
  -> Result<'b option, 'c>
Examples
Example 1
Assume that we have the following function:
// int -> int -> int -> int
let add a b c = a + b + c
Then using the infix operators, we can do the following:
// Ok (Some 42)
let opResult : Result<int option, string> =
  add
  <!> (Ok (Some 30)) 
  <*> (Ok (Some 10)) 
  <*> (Ok (Some 2)) 
If we have values that are not Option wrapped, we can use the <*^> operator:
let opResult : Result<int option, string> =
  add
  <!> (Ok (Some 30)) 
  <*^> (Ok 10) 
  <*> (Ok (Some 2))
Example 2
The ResultOption.map2 example can be written using the infix operators as below:
let toCreatePostRequest (dto : CreatePostRequestDto) = 
​
  // Result<Location option, string>
  let locationR = 
    location
    <!> Option.traverseResult Latitude.TryCreate dto.Latitude
    <*> Option.traverseResult Longitude.TryCreate dto.Longitude
​
  // Result<Tweet, string>
  let tweetR = Tweet.TryCreate dto.Tweet
​
  // Result<CreatePostRequest, string>
  Result.map2 createPostRequest tweetR locationR
map3
zip
Last modified 2mo ago