File Paths in F#

open System
open System.IO

// The Path module provides functions to parse and construct file paths
// in a way that is portable between operating systems.

// Join should be used to construct paths in a portable way.
// It takes any number of arguments and constructs a hierarchical path from them.
let p = Path.Combine("dir1", "dir2", "filename")
printfn "p: %s" p

// You should always use Path.Combine instead of concatenating
// separators manually. In addition to providing portability,
// Path.Combine will also normalize paths by removing superfluous
// separators and directory changes.
printfn "%s" (Path.Combine("dir1//", "filename"))
printfn "%s" (Path.Combine("dir1/../dir1", "filename"))

// GetDirectoryName and GetFileName can be used to split a path to the
// directory and the file. 
printfn "GetDirectoryName(p): %s" (Path.GetDirectoryName(p))
printfn "GetFileName(p): %s" (Path.GetFileName(p))

// We can check whether a path is absolute.
printfn "%b" (Path.IsPathRooted("dir/file"))
printfn "%b" (Path.IsPathRooted("/dir/file"))

let filename = "config.json"

// Some file names have extensions following a dot.
// We can split the extension out of such names with GetExtension.
let ext = Path.GetExtension(filename)
printfn "%s" ext

// To find the file's name with the extension removed,
// use GetFileNameWithoutExtension.
printfn "%s" (Path.GetFileNameWithoutExtension(filename))

// GetRelativePath finds a relative path between a base and a target.
// It returns an empty string if the target cannot be made relative to base.
let rel = Path.GetRelativePath("a/b", "a/b/t/file")
printfn "%s" rel

let rel2 = Path.GetRelativePath("a/b", "a/c/t/file")
printfn "%s" rel2

This F# code demonstrates file path operations using the System.IO.Path module, which provides similar functionality to Go’s filepath package. Here are some key points:

Path.Combine is used to join path components, similar to filepath.Join in Go.
Path.GetDirectoryName and Path.GetFileName are used to split a path into directory and file components, analogous to filepath.Dir and filepath.Base.
Path.IsPathRooted checks if a path is absolute, similar to filepath.IsAbs.
Path.GetExtension extracts the file extension, like filepath.Ext.
Path.GetFileNameWithoutExtension removes the extension from a filename, which is similar to using strings.TrimSuffix with the extension in Go.
Path.GetRelativePath finds a relative path between two paths, analogous to filepath.Rel.

Note that F# uses different naming conventions (PascalCase for functions) and has some slightly different behaviors. For example, Path.GetRelativePath returns an empty string instead of an error when a relative path can’t be computed.

To run this F# program, you would typically save it as a .fsx file and use the F# interactive or compile it with the F# compiler.

$ dotnet fsi file-paths.fsx

$ dotnet fsc file-paths.fsx
$ dotnet file-paths.exe

This will output the results of the various file path operations, demonstrating how to work with file paths in a cross-platform manner using F#.

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File Paths in F#