bind f inp evaluates to match inp with Error e -> Error e | Ok x -> f x

binder : 'T -> Result<'U, 'TError>

A function that takes the value of type T from a result and transforms it into a result containing a value of type U.

result : Result<'T, 'TError>

The input result.

Returns: Result<'U, 'TError>

A result of the output type of the binder.

Example

 let tryParse (input: string) =
     match System.Int32.TryParse input with
     | true, v -> Ok v
     | false, _ -> Error "couldn't parse"

 Error "message" |> Result.bind tryParse // evaluates to Error "message"

 Ok "42" |> Result.bind tryParse // evaluates to Ok 42

 Ok "Forty-two" |> Result.bind tryParse // evaluates to Error "couldn't parse"

Evaluates to true if result is Ok and its value is equal to value.

value : 'T

The value to test for equality.

result : Result<'T, 'Error>

The input result.

Returns: bool

True if the result is Ok and contains a value equal to value, otherwise false.

Example

 (99, Error 99) ||> Result.contains // evaluates to false
 (99, Ok 99) ||> Result.contains // evaluates to true
 (99, Ok 100) ||> Result.contains // evaluates to false

count inp evaluates to match inp with Error _ -> 0 | Ok _ -> 1.

result : Result<'T, 'Error>

The input result.

Returns: int

A zero if the result is Error, a one otherwise.

Example

 Error 99 |> Result.count // evaluates to 0
 Ok 99 |> Result.count // evaluates to 1

Gets the value of the result if the result is Ok, otherwise returns the specified default value.

value : 'T

The specified default value.

result : Result<'T, 'Error>

The input result.

Returns: 'T

The result if the result is Ok, else the default value.

Example

 Result.defaultValue 2 (Error 3) // evaluates to 2
 Result.defaultValue 2 (Ok 1) // evaluates to 1

Gets the value of the result if the result is Ok, otherwise evaluates defThunk and returns the result.

defThunk is not evaluated unless result is Error.

defThunk : 'Error -> 'T

A thunk that provides a default value when evaluated.

result : Result<'T, 'Error>

The input result.

Returns: 'T

The result if the result is Ok, else the result of evaluating defThunk.

Example

 Ok 1 |> Result.defaultWith (fun error -> 99) // evaluates to 1
 Error 2 |> Result.defaultWith (fun error -> 99) // evaluates to 99

exists p inp evaluates to match inp with Error _ -> false | Ok x -> p x.

predicate : 'T -> bool

A function that evaluates to a boolean when given a value from the result type.

result : Result<'T, 'Error>

The input result.

Returns: bool

False if the result is Error, otherwise it returns the result of applying the predicate to the result value.

Example

 Error 6 |> Result.exists (fun x -> x >= 5) // evaluates to false
 Ok 42 |> Result.exists (fun x -> x >= 5) // evaluates to true
 Ok 4 |> Result.exists (fun x -> x >= 5) // evaluates to false

fold f s inp evaluates to match inp with Error _ -> s | Ok x -> f s x.

folder : 'State -> 'T -> 'State

A function to update the state data when given a value from an result.

state : 'State

The initial state.

result : Result<'T, 'Error>

The input result.

Returns: 'State

The original state if the result is Error, otherwise it returns the updated state with the folder and the result value.

Example

 (0, Error 2) ||> Result.fold (fun accum x -> accum + x * 2) // evaluates to 0
 (0, Ok 1) ||> Result.fold (fun accum x -> accum + x * 2) // evaluates to 2
 (10, Ok 1) ||> Result.fold (fun accum x -> accum + x * 2) // evaluates to 12

fold f inp s evaluates to match inp with Error _ -> s | Ok x -> f x s.

folder : 'T -> 'State -> 'State

A function to update the state data when given a value from an result.

result : Result<'T, 'Error>

The input result.

state : 'State

The initial state.

Returns: 'State

The original state if the result is Error, otherwise it returns the updated state with the folder and the result value.

Example

 (Error 2, 0) ||> Result.foldBack (fun x accum -> accum + x * 2) // evaluates to 0
 (Ok 1, 0) ||> Result.foldBack (fun x accum -> accum + x * 2) // evaluates to 2
 (Ok 1, 10) ||> Result.foldBack (fun x accum -> accum + x * 2) // evaluates to 12

forall p inp evaluates to match inp with Error _ -> true | Ok x -> p x.

predicate : 'T -> bool

A function that evaluates to a boolean when given a value from the result type.

result : Result<'T, 'Error>

The input result.

Returns: bool

True if the result is Error, otherwise it returns the result of applying the predicate to the result value.

Example

 Error 1 |> Result.forall (fun x -> x >= 5) // evaluates to true
 Ok 42 |> Result.forall (fun x -> x >= 5) // evaluates to true
 Ok 4 |> Result.forall (fun x -> x >= 5) // evaluates to false

Returns true if the result is Error.

result : Result<'T, 'Error>

The input result.

Returns: bool

True if the result is Error.

Example

 Ok 42 |> Result.isError // evaluates to false
 Error 42 |> Result.isError // evaluates to true

Returns true if the result is Ok.

result : Result<'T, 'Error>

The input result.

Returns: bool

True if the result is OK.

Example

 Ok 42 |> Result.isOk // evaluates to true
 Error 42 |> Result.isOk // evaluates to false

iter f inp executes match inp with Error _ -> () | Ok x -> f x.

action : 'T -> unit

A function to apply to the result value.

result : Result<'T, 'Error>

The input result.

Example

 Error "Hello world" |> Result.iter (printfn "%s") // does nothing
 Ok "Hello world" |> Result.iter (printfn "%s") // prints "Hello world"

map f inp evaluates to match inp with Error e -> Error e | Ok x -> Ok (f x).

mapping : 'T -> 'U

A function to apply to the OK result value.

result : Result<'T, 'TError>

The input result.

Returns: Result<'U, 'TError>

A result of the input value after applying the mapping function, or Error if the input is Error.

Example

 Ok 1 |> Result.map (fun x -> "perfect") // evaluates to Ok "perfect"

 Error "message" |> Result.map (fun x -> "perfect") // evaluates to Error "message"

map f inp evaluates to match inp with Error x -> Error (f x) | Ok v -> Ok v.

mapping : 'TError -> 'U

A function to apply to the Error result value.

result : Result<'T, 'TError>

The input result.

Returns: Result<'T, 'U>

A result of the error value after applying the mapping function, or Ok if the input is Ok.

Example

 Ok 1 |> Result.mapError (fun x -> "bar") // evaluates to Ok 1

 Error "foo" |> Result.mapError (fun x -> "bar") // evaluates to Error "bar"

Convert the result to an array of length 0 or 1.

result : Result<'T, 'Error>

The input result.

Returns: 'T[]

The result array.

Example

 Error 42 |> Result.toArray // evaluates to [||]
 Ok 42 |> Result.toArray // evaluates to [| 42 |]

Convert the result to a list of length 0 or 1.

result : Result<'T, 'Error>

The input result.

Returns: List<'T>

The result list.

Example

 Error 42 |> Result.toList // evaluates to []
 Ok 42 |> Result.toList // evaluates to [ 42 ]

Convert the result to an Option value.

result : Result<'T, 'Error>

The input result.

Returns: Option<'T>

The option value.

Example

 Error 42 |> Result.toOption // evaluates to None
 Ok 42 |> Result.toOption // evaluates to Some 42

Convert the result to an Option value.

result : Result<'T, 'Error>

The input result.

Returns: ValueOption<'T>

The result value.

Example

 Error 42 |> Result.toOption // evaluates to ValueNone
 Ok 42 |> Result.toOption // evaluates to ValueSome 42