Result (FSharp.Core) | FSharp.Core

FSharp.Core

Result Module

Namespace: FSharp.Core
Assembly: FSharp.Core.dll

Contains operations for working with values of type Result.

Functions and values

Function or value	Description
`bind binder result` Full Usage: `bind binder result` Parameters: 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. Modifiers: inline Type parameters: 'T, 'U, 'TError	`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"` val tryParse: input: string -> Result<int,string> val input: string Multiple items val string: value: 'T -> string -------------------- type string = System.String namespace System [<Struct>] type Int32 = member CompareTo: value: int -> int + 1 overload member Equals: obj: int -> bool + 1 overload member GetHashCode: unit -> int member GetTypeCode: unit -> TypeCode member ToString: unit -> string + 3 overloads member TryFormat: utf8Destination: Span<byte> * bytesWritten: byref<int> * ?format: ReadOnlySpan<char> * ?provider: IFormatProvider -> bool + 1 overload static member Abs: value: int -> int static member BigMul: left: int * right: int -> int64 static member Clamp: value: int * min: int * max: int -> int static member CopySign: value: int * sign: int -> int ... <summary>Represents a 32-bit signed integer.</summary> System.Int32.TryParse(s: string, result: byref<int>) : bool System.Int32.TryParse(s: System.ReadOnlySpan<char>, result: byref<int>) : bool System.Int32.TryParse(utf8Text: System.ReadOnlySpan<byte>, result: byref<int>) : bool System.Int32.TryParse(s: string, provider: System.IFormatProvider, result: byref<int>) : bool System.Int32.TryParse(s: System.ReadOnlySpan<char>, provider: System.IFormatProvider, result: byref<int>) : bool System.Int32.TryParse(utf8Text: System.ReadOnlySpan<byte>, provider: System.IFormatProvider, result: byref<int>) : bool System.Int32.TryParse(s: string, style: System.Globalization.NumberStyles, provider: System.IFormatProvider, result: byref<int>) : bool System.Int32.TryParse(s: System.ReadOnlySpan<char>, style: System.Globalization.NumberStyles, provider: System.IFormatProvider, result: byref<int>) : bool System.Int32.TryParse(utf8Text: System.ReadOnlySpan<byte>, style: System.Globalization.NumberStyles, provider: System.IFormatProvider, result: byref<int>) : bool val v: int union case Result.Ok: ResultValue: 'T -> Result<'T,'TError> union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val bind: binder: ('T -> Result<'U,'TError>) -> result: Result<'T,'TError> -> Result<'U,'TError>
`contains value result` Full Usage: `contains value result` Parameters: 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. Modifiers: inline Type parameters: 'T, 'Error	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` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val contains: value: 'T -> result: Result<'T,'Error> -> bool (requires equality) union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`count result` Full Usage: `count result` Parameters: result : `Result<'T, 'Error>` - The input result. Returns: `int` A zero if the result is Error, a one otherwise. Modifiers: inline Type parameters: 'T, 'Error	`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` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val count: result: Result<'T,'Error> -> int union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`defaultValue value result` Full Usage: `defaultValue value result` Parameters: 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. Modifiers: inline Type parameters: 'T, 'Error	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` Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val defaultValue: value: 'T -> result: Result<'T,'Error> -> 'T union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`defaultWith defThunk result` Full Usage: `defaultWith defThunk result` Parameters: 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. Modifiers: inline Type parameters: 'Error, 'T	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` union case Result.Ok: ResultValue: 'T -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val defaultWith: defThunk: ('Error -> 'T) -> result: Result<'T,'Error> -> 'T val error: obj union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> val error: int
`exists predicate result` Full Usage: `exists predicate result` Parameters: 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. Modifiers: inline Type parameters: 'T, 'Error	`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` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val exists: predicate: ('T -> bool) -> result: Result<'T,'Error> -> bool val x: int union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`fold folder state result` Full Usage: `fold folder state result` Parameters: 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. Modifiers: inline Type parameters: 'T, 'Error, 'State	`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` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val fold<'T,'Error,'State> : folder: ('State -> 'T -> 'State) -> state: 'State -> result: Result<'T,'Error> -> 'State val accum: int val x: int union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`foldBack folder result state` Full Usage: `foldBack folder result state` Parameters: 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. Modifiers: inline Type parameters: 'T, 'Error, 'State	`foldBack 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` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val foldBack<'T,'Error,'State> : folder: ('T -> 'State -> 'State) -> result: Result<'T,'Error> -> state: 'State -> 'State val x: int val accum: int union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`forall predicate result` Full Usage: `forall predicate result` Parameters: 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. Modifiers: inline Type parameters: 'T, 'Error	`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` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val forall: predicate: ('T -> bool) -> result: Result<'T,'Error> -> bool val x: int union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`isError result` Full Usage: `isError result` Parameters: result : `Result<'T, 'Error>` - The input result. Returns: `bool` True if the result is Error. Modifiers: inline Type parameters: 'T, 'Error	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` union case Result.Ok: ResultValue: 'T -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val isError: result: Result<'T,'Error> -> bool union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError>
`isOk result` Full Usage: `isOk result` Parameters: result : `Result<'T, 'Error>` - The input result. Returns: `bool` True if the result is OK. Modifiers: inline Type parameters: 'T, 'Error	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` union case Result.Ok: ResultValue: 'T -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val isOk: result: Result<'T,'Error> -> bool union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError>
`iter action result` Full Usage: `iter action result` Parameters: action : `'T -> unit` - A function to apply to the result value. result : `Result<'T, 'Error>` - The input result. Modifiers: inline Type parameters: 'T, 'Error	`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"` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val iter: action: ('T -> unit) -> result: Result<'T,'Error> -> unit val printfn: format: Printf.TextWriterFormat<'T> -> 'T union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`map mapping result` Full Usage: `map mapping result` Parameters: 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. Modifiers: inline Type parameters: 'T, 'U, 'TError	`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"` union case Result.Ok: ResultValue: 'T -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val map: mapping: ('T -> 'U) -> result: Result<'T,'TError> -> Result<'U,'TError> val x: int union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> val x: obj
`mapError mapping result` Full Usage: `mapError mapping result` Parameters: 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. Modifiers: inline Type parameters: 'TError, 'U, 'T	`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"` union case Result.Ok: ResultValue: 'T -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val mapError: mapping: ('TError -> 'U) -> result: Result<'T,'TError> -> Result<'T,'U> val x: obj union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> val x: string
`toArray result` Full Usage: `toArray result` Parameters: result : `Result<'T, 'Error>` - The input result. Returns: `'T array` The result array. Modifiers: inline Type parameters: 'T, 'Error	Convert the result to an array of length 0 or 1. result : `Result<'T, 'Error>` The input result. Returns: `'T array` The result array. Example `Error 42 \|> Result.toArray // evaluates to [\|\|] Ok 42 \|> Result.toArray // evaluates to [\| 42 \|]` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val toArray: result: Result<'T,'Error> -> 'T array union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`toList result` Full Usage: `toList result` Parameters: result : `Result<'T, 'Error>` - The input result. Returns: `'T list` The result list. Modifiers: inline Type parameters: 'T, 'Error	Convert the result to a list of length 0 or 1. result : `Result<'T, 'Error>` The input result. Returns: `'T list` The result list. Example `Error 42 \|> Result.toList // evaluates to [] Ok 42 \|> Result.toList // evaluates to [ 42 ]` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val toList: result: Result<'T,'Error> -> 'T list union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`toOption result` Full Usage: `toOption result` Parameters: result : `Result<'T, 'Error>` - The input result. Returns: `'T option` The option value. Modifiers: inline Type parameters: 'T, 'Error	Convert the result to an Option value. result : `Result<'T, 'Error>` The input result. Returns: `'T option` The option value. Example `Error 42 \|> Result.toOption // evaluates to None Ok 42 \|> Result.toOption // evaluates to Some 42` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val toOption: result: Result<'T,'Error> -> 'T option union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>
`toValueOption result` Full Usage: `toValueOption result` Parameters: result : `Result<'T, 'Error>` - The input result. Returns: `'T voption` The result value. Modifiers: inline Type parameters: 'T, 'Error	Convert the result to an Option value. result : `Result<'T, 'Error>` The input result. Returns: `'T voption` The result value. Example `Error 42 \|> Result.toOption // evaluates to ValueNone Ok 42 \|> Result.toOption // evaluates to ValueSome 42` union case Result.Error: ErrorValue: 'TError -> Result<'T,'TError> Multiple items module Result from Microsoft.FSharp.Core -------------------- [<Struct>] type Result<'T,'TError> = \| Ok of ResultValue: 'T \| Error of ErrorValue: 'TError val toOption: result: Result<'T,'Error> -> 'T option union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>