FSharp Functional Programming—Literals

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F# Functional Programming Identifiers Keywords Literals Values and Functions Scope Recursion Anonymous Functions Operators Lists List Comprehensions Control Flow Types and Type Inference Pattern Matching Defining Types Exception Handling Lazy Evaluation Summary

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© 2007 Robert Pickering

Literals

Literals represent constant values and are useful building blocks for computations. F# has a rich set of literals, summarized in Table 3-1.

Table 3-1. F# Literals

Example	F# Type	.NET Type	Description
"Hello\t ", "World\n"	string	System.String	A string in which a backslash (\) is an escape character
@"c:\dir\fs", @""""	string	System.String	A verbatim string where a backslash (\) is a regular character
"bytesbytesbytes"B	byte array	System.Byte[]	A string that will be stored as a byte array
'c'	char	System.Char	A character
true, false	bool	System.Boolean	A Boolean
0x22	int/int32	System.Int32	An integer as a hexadecimal
0o42	int/int32	System.Int32	An integer as an octal
0b10010	int/ int32	System.Int32	An integer as a binary
34y	sbyte	System.SByte	A signed byte
34uy	byte	System.Byte	An unsigned byte
34s	int16	System.Int16	A 16-bit integer
34us	uint16	System.UInt16	An unsigned 16-bit integer
34l	int/int32	System.Int32	A 32-bit integer
34ul	uint32	System.UInt32	An unsigned 32-bit integer
34n	nativeint	System.IntPtr	A native-sized integer
34un	unativeint	System.UIntPtr	An unsigned native-sized integer
34L	int64	System.Int64	A 32-bit integer
34UL	uint64	System.Int64	An unsigned 32-bit integer
3.0F, 3.0f	float32	System.Single	A 32-bit IEEE floating-point number
3.0	float	System.Double	A 64-bit IEEE floating-point number
3474262622571I	bigint	Microsoft.FSharp.Math.BigInt	An arbitrary large integer
474262612536171N	bignum	Microsoft.FSharp.Math.BigNum	An arbitrary large number

In F# string literals can contain newline characters, and regular string literals can contain standard escape codes. Verbatim string literals use a backslash (\) as a regular character, and two double quotes ("") are the escape for a quote. You can define all integer types using hexadecimal and octal by using the appropriate prefix and postfix. The following example shows some of these literals in action, along with how to use the F# printf function with a %A pattern to output them to the console. The printf function interprets the %A format pattern using a combination of F#’s reflection and the .NET ToString method, which is available for every type, to output values in a readable way. You can also access this functionality by using the print_any and any_to_string functions from the F# library.

#light
let message = "Hello
        World\r\n\t!"
let dir = @"c:\projects"
 
let bytes = "bytesbytesbytes"B
 
let xA = 0xFFy
let xB = 0o7777un
let xC = 0b10010UL
 
let print x = printfn "%A" x
 
let main() =
    print message;
    print dir;
    print bytes;
    print xA;
    print xB;
    print xC
 
main()

The results of this example, when compiled and executed, are as follows:

---

"Hello\n World\r\n\t!"
"c:\\projects"
[|98uy; 121uy; 116uy; 101uy; 115uy; 98uy; 121uy; 116uy; 101uy; 115uy; 98uy;
121uy; 116uy; 101uy; 115uy|]
-1y
4095
18UL

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