Printf (FSharp.Core) | FSharp.Core

FSharp.Core

Printf Module

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

Extensible printf-style formatting for numbers and other datatypes

Format specifications are strings with "%" markers indicating format placeholders. Format placeholders consist of %[flags][width][.precision][type].

Types

Type	Description
BuilderFormat<'T, 'Result>	Represents a statically-analyzed format associated with writing to a StringBuilder. The first type parameter indicates the arguments of the format operation and the last the overall return type.
BuilderFormat<'T>	Represents a statically-analyzed format associated with writing to a StringBuilder. The type parameter indicates the arguments and return type of the format operation.
StringFormat<'T, 'Result>	Represents a statically-analyzed format when formatting builds a string. The first type parameter indicates the arguments of the format operation and the last the overall return type.
StringFormat<'T>	Represents a statically-analyzed format when formatting builds a string. The type parameter indicates the arguments and return type of the format operation.
TextWriterFormat<'T, 'Result>	Represents a statically-analyzed format associated with writing to a TextWriter. The first type parameter indicates the arguments of the format operation and the last the overall return type.
TextWriterFormat<'T>	Represents a statically-analyzed format associated with writing to a TextWriter. The type parameter indicates the arguments and return type of the format operation.

Functions and values

Function or value	Description
`bprintf builder format` Full Usage: `bprintf builder format` Parameters: builder : `StringBuilder` - The StringBuilder to print to. format : `BuilderFormat<'T>` - The input format or interpolated string. Returns: `'T` The return type and arguments of the formatter.	Print to a StringBuilder builder : `StringBuilder` The StringBuilder to print to. format : `BuilderFormat<'T>` The input format or interpolated string. Returns: `'T` The return type and arguments of the formatter. Example Using interpolated strings: `open Printf open System.Text let buffer = new StringBuilder() bprintf buffer $"Write three = {1+2}" buffer.ToString()` module Printf from Microsoft.FSharp.Core namespace System namespace System.Text val buffer: StringBuilder Multiple items type StringBuilder = interface ISerializable new: unit -> unit + 5 overloads member Append: value: bool -> StringBuilder + 25 overloads member AppendFormat: provider: IFormatProvider * format: string * arg0: obj -> StringBuilder + 14 overloads member AppendJoin: separator: char * [<ParamArray>] values: obj array -> StringBuilder + 9 overloads member AppendLine: unit -> StringBuilder + 3 overloads member Clear: unit -> StringBuilder member CopyTo: sourceIndex: int * destination: char array * destinationIndex: int * count: int -> unit + 1 overload member EnsureCapacity: capacity: int -> int member Equals: span: ReadOnlySpan<char> -> bool + 1 overload ... <summary>Represents a mutable string of characters. This class cannot be inherited.</summary> -------------------- StringBuilder() : StringBuilder StringBuilder(capacity: int) : StringBuilder StringBuilder(value: string) : StringBuilder StringBuilder(capacity: int, maxCapacity: int) : StringBuilder StringBuilder(value: string, capacity: int) : StringBuilder StringBuilder(value: string, startIndex: int, length: int, capacity: int) : StringBuilder val bprintf: builder: StringBuilder -> format: BuilderFormat<'T> -> 'T StringBuilder.ToString() : string StringBuilder.ToString(startIndex: int, length: int) : string Evaluates to `"Write three = 3"`. Example Using `%` format patterns: `open Printf open System.Text let buffer = new StringBuilder() bprintf buffer "Write five = %d" (3+2) buffer.ToString()` module Printf from Microsoft.FSharp.Core namespace System namespace System.Text val buffer: StringBuilder Multiple items type StringBuilder = interface ISerializable new: unit -> unit + 5 overloads member Append: value: bool -> StringBuilder + 25 overloads member AppendFormat: provider: IFormatProvider * format: string * arg0: obj -> StringBuilder + 14 overloads member AppendJoin: separator: char * [<ParamArray>] values: obj array -> StringBuilder + 9 overloads member AppendLine: unit -> StringBuilder + 3 overloads member Clear: unit -> StringBuilder member CopyTo: sourceIndex: int * destination: char array * destinationIndex: int * count: int -> unit + 1 overload member EnsureCapacity: capacity: int -> int member Equals: span: ReadOnlySpan<char> -> bool + 1 overload ... <summary>Represents a mutable string of characters. This class cannot be inherited.</summary> -------------------- StringBuilder() : StringBuilder StringBuilder(capacity: int) : StringBuilder StringBuilder(value: string) : StringBuilder StringBuilder(capacity: int, maxCapacity: int) : StringBuilder StringBuilder(value: string, capacity: int) : StringBuilder StringBuilder(value: string, startIndex: int, length: int, capacity: int) : StringBuilder val bprintf: builder: StringBuilder -> format: BuilderFormat<'T> -> 'T StringBuilder.ToString() : string StringBuilder.ToString(startIndex: int, length: int) : string Evaluates to `"Write five = 5"`.
`eprintf format` Full Usage: `eprintf format` Parameters: format : `TextWriterFormat<'T>` - The input formatter. Returns: `'T` The return type and arguments of the formatter.	Formatted printing to stderr format : `TextWriterFormat<'T>` The input formatter. Returns: `'T` The return type and arguments of the formatter. Example Using interpolated strings: `eprintf $"Write three = {1+2}"` val eprintf: format: Printf.TextWriterFormat<'T> -> 'T After evaluation the text `"Write three = 3"` is written to `stderr`. Example Using `%` format patterns: `eprintf "Write five = %d" (3+2)` val eprintf: format: Printf.TextWriterFormat<'T> -> 'T After evaluation the text `"Write five = 5"` is written to `stderr`.
`eprintfn format` Full Usage: `eprintfn format` Parameters: format : `TextWriterFormat<'T>` - The input formatter. Returns: `'T` The return type and arguments of the formatter.	Formatted printing to stderr, adding a newline format : `TextWriterFormat<'T>` The input formatter. Returns: `'T` The return type and arguments of the formatter. Example Using interpolated strings: `eprintfn $"Write three = {1+2}" eprintfn $"Write four = {2+2}"` val eprintfn: format: Printf.TextWriterFormat<'T> -> 'T After evaluation two lines are written to `stderr`. Example Using `%` format patterns: `eprintfn "Write five = %d" (3+2) eprintfn "Write six = %d" (3+3)` val eprintfn: format: Printf.TextWriterFormat<'T> -> 'T After evaluation two lines are written to `stderr`.
`failwithf format` Full Usage: `failwithf format` Parameters: format : `StringFormat<'T, 'Result>` - The input formatter. Returns: `'T` The arguments of the formatter.	Print to a string buffer and raise an exception with the given result. Helper printers must return strings. format : `StringFormat<'T, 'Result>` The input formatter. Returns: `'T` The arguments of the formatter. Example `failwithf "That's wrong. Five = %d and six = %d" (3+2) (3+3)` val failwithf: format: Printf.StringFormat<'T,'Result> -> 'T Throws `Exception` with message `"That's wrong. Five = 5 and six = 6"`.
`fprintf textWriter format` Full Usage: `fprintf textWriter format` Parameters: textWriter : `TextWriter` - The TextWriter to print to. format : `TextWriterFormat<'T>` - The input formatter. Returns: `'T` The return type and arguments of the formatter.	Print to a text writer. textWriter : `TextWriter` The TextWriter to print to. format : `TextWriterFormat<'T>` The input formatter. Returns: `'T` The return type and arguments of the formatter. Example Using interpolated strings: `open Printf open System.IO let file = File.CreateText("out.txt") fprintf file $"Write three = {1+2}" file.Close()` module Printf from Microsoft.FSharp.Core namespace System namespace System.IO val file: StreamWriter type File = static member AppendAllBytes: path: string * bytes: byte array -> unit + 1 overload static member AppendAllBytesAsync: path: string * bytes: byte array * ?cancellationToken: CancellationToken -> Task + 1 overload static member AppendAllLines: path: string * contents: IEnumerable<string> -> unit + 1 overload static member AppendAllLinesAsync: path: string * contents: IEnumerable<string> * encoding: Encoding * ?cancellationToken: CancellationToken -> Task + 1 overload static member AppendAllText: path: string * contents: string -> unit + 3 overloads static member AppendAllTextAsync: path: string * contents: string * encoding: Encoding * ?cancellationToken: CancellationToken -> Task + 3 overloads static member AppendText: path: string -> StreamWriter static member Copy: sourceFileName: string * destFileName: string -> unit + 1 overload static member Create: path: string -> FileStream + 2 overloads static member CreateSymbolicLink: path: string * pathToTarget: string -> FileSystemInfo ... <summary>Provides static methods for the creation, copying, deletion, moving, and opening of a single file, and aids in the creation of <see cref="T:System.IO.FileStream" /> objects.</summary> File.CreateText(path: string) : StreamWriter val fprintf: textWriter: TextWriter -> format: TextWriterFormat<'T> -> 'T StreamWriter.Close() : unit After evaluation the file contains the text `"Write three = 3"`. Example Using `%` format patterns: `open Printf open System.IO let file = File.CreateText("out.txt") fprintf file "Write five = %d" (3+2) file.Close()` module Printf from Microsoft.FSharp.Core namespace System namespace System.IO val file: StreamWriter type File = static member AppendAllBytes: path: string * bytes: byte array -> unit + 1 overload static member AppendAllBytesAsync: path: string * bytes: byte array * ?cancellationToken: CancellationToken -> Task + 1 overload static member AppendAllLines: path: string * contents: IEnumerable<string> -> unit + 1 overload static member AppendAllLinesAsync: path: string * contents: IEnumerable<string> * encoding: Encoding * ?cancellationToken: CancellationToken -> Task + 1 overload static member AppendAllText: path: string * contents: string -> unit + 3 overloads static member AppendAllTextAsync: path: string * contents: string * encoding: Encoding * ?cancellationToken: CancellationToken -> Task + 3 overloads static member AppendText: path: string -> StreamWriter static member Copy: sourceFileName: string * destFileName: string -> unit + 1 overload static member Create: path: string -> FileStream + 2 overloads static member CreateSymbolicLink: path: string * pathToTarget: string -> FileSystemInfo ... <summary>Provides static methods for the creation, copying, deletion, moving, and opening of a single file, and aids in the creation of <see cref="T:System.IO.FileStream" /> objects.</summary> File.CreateText(path: string) : StreamWriter val fprintf: textWriter: TextWriter -> format: TextWriterFormat<'T> -> 'T StreamWriter.Close() : unit After evaluation the file contains the text `"Write five = 5"`.
`fprintfn textWriter format` Full Usage: `fprintfn textWriter format` Parameters: textWriter : `TextWriter` - The TextWriter to print to. format : `TextWriterFormat<'T>` - The input formatter. Returns: `'T` The return type and arguments of the formatter.	Print to a text writer, adding a newline textWriter : `TextWriter` The TextWriter to print to. format : `TextWriterFormat<'T>` The input formatter. Returns: `'T` The return type and arguments of the formatter. Example Using interpolated strings: `open Printf open System.IO let file = File.CreateText("out.txt") fprintfn file $"Write three = {1+2}" fprintfn file $"Write four = {2+2}" file.Close()` module Printf from Microsoft.FSharp.Core namespace System namespace System.IO val file: StreamWriter type File = static member AppendAllBytes: path: string * bytes: byte array -> unit + 1 overload static member AppendAllBytesAsync: path: string * bytes: byte array * ?cancellationToken: CancellationToken -> Task + 1 overload static member AppendAllLines: path: string * contents: IEnumerable<string> -> unit + 1 overload static member AppendAllLinesAsync: path: string * contents: IEnumerable<string> * encoding: Encoding * ?cancellationToken: CancellationToken -> Task + 1 overload static member AppendAllText: path: string * contents: string -> unit + 3 overloads static member AppendAllTextAsync: path: string * contents: string * encoding: Encoding * ?cancellationToken: CancellationToken -> Task + 3 overloads static member AppendText: path: string -> StreamWriter static member Copy: sourceFileName: string * destFileName: string -> unit + 1 overload static member Create: path: string -> FileStream + 2 overloads static member CreateSymbolicLink: path: string * pathToTarget: string -> FileSystemInfo ... <summary>Provides static methods for the creation, copying, deletion, moving, and opening of a single file, and aids in the creation of <see cref="T:System.IO.FileStream" /> objects.</summary> File.CreateText(path: string) : StreamWriter val fprintfn: textWriter: TextWriter -> format: TextWriterFormat<'T> -> 'T StreamWriter.Close() : unit After evaluation the file contains two lines. Example Using `%` format patterns: `open Printf open System.IO let file = File.CreateText("out.txt") fprintfn file "Write five = %d" (3+2) fprintfn file "Write six = %d" (3+3) file.Close()` module Printf from Microsoft.FSharp.Core namespace System namespace System.IO val file: StreamWriter type File = static member AppendAllBytes: path: string * bytes: byte array -> unit + 1 overload static member AppendAllBytesAsync: path: string * bytes: byte array * ?cancellationToken: CancellationToken -> Task + 1 overload static member AppendAllLines: path: string * contents: IEnumerable<string> -> unit + 1 overload static member AppendAllLinesAsync: path: string * contents: IEnumerable<string> * encoding: Encoding * ?cancellationToken: CancellationToken -> Task + 1 overload static member AppendAllText: path: string * contents: string -> unit + 3 overloads static member AppendAllTextAsync: path: string * contents: string * encoding: Encoding * ?cancellationToken: CancellationToken -> Task + 3 overloads static member AppendText: path: string -> StreamWriter static member Copy: sourceFileName: string * destFileName: string -> unit + 1 overload static member Create: path: string -> FileStream + 2 overloads static member CreateSymbolicLink: path: string * pathToTarget: string -> FileSystemInfo ... <summary>Provides static methods for the creation, copying, deletion, moving, and opening of a single file, and aids in the creation of <see cref="T:System.IO.FileStream" /> objects.</summary> File.CreateText(path: string) : StreamWriter val fprintfn: textWriter: TextWriter -> format: TextWriterFormat<'T> -> 'T StreamWriter.Close() : unit After evaluation the file contains two lines.
`kbprintf continuation builder format` Full Usage: `kbprintf continuation builder format` Parameters: continuation : `unit -> 'Result` - The function called after formatting to generate the format result. builder : `StringBuilder` - The input StringBuilder. format : `BuilderFormat<'T, 'Result>` - The input formatter. Returns: `'T` The arguments of the formatter.	bprintf, but call the given 'final' function to generate the result. See `kprintf`. continuation : `unit -> 'Result` The function called after formatting to generate the format result. builder : `StringBuilder` The input StringBuilder. format : `BuilderFormat<'T, 'Result>` The input formatter. Returns: `'T` The arguments of the formatter. Example Using `%` format patterns: `open Printf open System.Text let buffer = new StringBuilder() kbprintf (fun () -> buffer.ToString()) buffer "Write five = %d" (3+2)` module Printf from Microsoft.FSharp.Core namespace System namespace System.Text val buffer: StringBuilder Multiple items type StringBuilder = interface ISerializable new: unit -> unit + 5 overloads member Append: value: bool -> StringBuilder + 25 overloads member AppendFormat: provider: IFormatProvider * format: string * arg0: obj -> StringBuilder + 14 overloads member AppendJoin: separator: char * [<ParamArray>] values: obj array -> StringBuilder + 9 overloads member AppendLine: unit -> StringBuilder + 3 overloads member Clear: unit -> StringBuilder member CopyTo: sourceIndex: int * destination: char array * destinationIndex: int * count: int -> unit + 1 overload member EnsureCapacity: capacity: int -> int member Equals: span: ReadOnlySpan<char> -> bool + 1 overload ... <summary>Represents a mutable string of characters. This class cannot be inherited.</summary> -------------------- StringBuilder() : StringBuilder StringBuilder(capacity: int) : StringBuilder StringBuilder(value: string) : StringBuilder StringBuilder(capacity: int, maxCapacity: int) : StringBuilder StringBuilder(value: string, capacity: int) : StringBuilder StringBuilder(value: string, startIndex: int, length: int, capacity: int) : StringBuilder val kbprintf: continuation: (unit -> 'Result) -> builder: StringBuilder -> format: BuilderFormat<'T,'Result> -> 'T StringBuilder.ToString() : string StringBuilder.ToString(startIndex: int, length: int) : string Evaluates to `"Write five = 5"`.
`kfprintf continuation textWriter format` Full Usage: `kfprintf continuation textWriter format` Parameters: continuation : `unit -> 'Result` - The function called after formatting to generate the format result. textWriter : `TextWriter` - The input TextWriter. format : `TextWriterFormat<'T, 'Result>` - The input formatter. Returns: `'T` The arguments of the formatter.	fprintf, but call the given 'final' function to generate the result. See `kprintf`. continuation : `unit -> 'Result` The function called after formatting to generate the format result. textWriter : `TextWriter` The input TextWriter. format : `TextWriterFormat<'T, 'Result>` The input formatter. Returns: `'T` The arguments of the formatter. Example Using `%` format patterns: `open Printf open System.IO let file = File.CreateText("out.txt") kfprintf (fun () -> file.Close()) file $"Write three = {1+2}"` module Printf from Microsoft.FSharp.Core namespace System namespace System.IO val file: StreamWriter type File = static member AppendAllBytes: path: string * bytes: byte array -> unit + 1 overload static member AppendAllBytesAsync: path: string * bytes: byte array * ?cancellationToken: CancellationToken -> Task + 1 overload static member AppendAllLines: path: string * contents: IEnumerable<string> -> unit + 1 overload static member AppendAllLinesAsync: path: string * contents: IEnumerable<string> * encoding: Encoding * ?cancellationToken: CancellationToken -> Task + 1 overload static member AppendAllText: path: string * contents: string -> unit + 3 overloads static member AppendAllTextAsync: path: string * contents: string * encoding: Encoding * ?cancellationToken: CancellationToken -> Task + 3 overloads static member AppendText: path: string -> StreamWriter static member Copy: sourceFileName: string * destFileName: string -> unit + 1 overload static member Create: path: string -> FileStream + 2 overloads static member CreateSymbolicLink: path: string * pathToTarget: string -> FileSystemInfo ... <summary>Provides static methods for the creation, copying, deletion, moving, and opening of a single file, and aids in the creation of <see cref="T:System.IO.FileStream" /> objects.</summary> File.CreateText(path: string) : StreamWriter val kfprintf: continuation: (unit -> 'Result) -> textWriter: TextWriter -> format: TextWriterFormat<'T,'Result> -> 'T StreamWriter.Close() : unit Writes `"Write three = 3"` to `out.txt`.
`kprintf continuation format` Full Usage: `kprintf continuation format` Parameters: continuation : `string -> 'Result` - The function called after formatting to generate the format result. format : `StringFormat<'T, 'Result>` - The input formatter. Returns: `'T` The arguments of the formatter.	printf, but call the given 'final' function to generate the result. For example, these let the printing force a flush after all output has been entered onto the channel, but not before. continuation : `string -> 'Result` The function called after formatting to generate the format result. format : `StringFormat<'T, 'Result>` The input formatter. Returns: `'T` The arguments of the formatter. Example Using `%` format patterns: `open Printf kprintf (fun s -> s + ", done!") $"Write three = {1+2}"` module Printf from Microsoft.FSharp.Core val kprintf: continuation: (string -> 'Result) -> format: StringFormat<'T,'Result> -> 'T val s: string Evaluates to `"Write three = 3, done!"`.
`ksprintf continuation format` Full Usage: `ksprintf continuation format` Parameters: continuation : `string -> 'Result` - The function called to generate a result from the formatted string. format : `StringFormat<'T, 'Result>` - The input formatter. Returns: `'T` The arguments of the formatter.	sprintf, but call the given 'final' function to generate the result. See `kprintf`. continuation : `string -> 'Result` The function called to generate a result from the formatted string. format : `StringFormat<'T, 'Result>` The input formatter. Returns: `'T` The arguments of the formatter. Example Using `%` format patterns: `open Printf ksprintf (fun s -> s + ", done!") $"Write three = {1+2}"` module Printf from Microsoft.FSharp.Core val ksprintf: continuation: (string -> 'Result) -> format: StringFormat<'T,'Result> -> 'T val s: string Evaluates to `"Write three = 3, done!"`.
`printf format` Full Usage: `printf format` Parameters: format : `TextWriterFormat<'T>` - The input formatter. Returns: `'T` The return type and arguments of the formatter.	Formatted printing to stdout format : `TextWriterFormat<'T>` The input formatter. Returns: `'T` The return type and arguments of the formatter. Example Using interpolated strings: `printf $"Write three = {1+2}"` val printf: format: Printf.TextWriterFormat<'T> -> 'T After evaluation the text `"Write three = 3"` is written to `stdout`. Example Using `%` format patterns: `printf "Write five = %d" (3+2)` val printf: format: Printf.TextWriterFormat<'T> -> 'T After evaluation the text `"Write five = 5"` is written to `stdout`.
`printfn format` Full Usage: `printfn format` Parameters: format : `TextWriterFormat<'T>` - The input formatter. Returns: `'T` The return type and arguments of the formatter.	Formatted printing to stdout, adding a newline. format : `TextWriterFormat<'T>` The input formatter. Returns: `'T` The return type and arguments of the formatter. Example Using interpolated strings: `printfn $"Write three = {1+2}" printfn $"Write four = {2+2}"` val printfn: format: Printf.TextWriterFormat<'T> -> 'T After evaluation the two lines are written to `stdout`. Example Using `%` format patterns: `printfn "Write five = %d" (3+2) printfn "Write six = %d" (3+3)` val printfn: format: Printf.TextWriterFormat<'T> -> 'T After evaluation the two lines are written to `stdout`.
`sprintf format` Full Usage: `sprintf format` Parameters: format : `StringFormat<'T>` - The input formatter. Returns: `'T` The formatted string.	Print to a string via an internal string buffer and return the result as a string. Helper printers must return strings. format : `StringFormat<'T>` The input formatter. Returns: `'T` The formatted string. Example `sprintf "Write five = %d and six = %d" (3+2) (3+3)` val sprintf: format: Printf.StringFormat<'T> -> 'T Evaluates to `"Write five = 5 and six = 6"`.