hpath/README.md

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Fork chrisdone's path library I wasn't happy with the way it dealt with Dir vs File things. In his version of the library, a `Path b Dir` always ends with a trailing path separator and `Path b File` never ends with a trailing path separator. IMO, it is nonsensical to make a Dir vs File distinction on path level, although it first seems nice. Some of the reasons are: * a path is just that: a path. It is completely disconnected from IO level and even if a `Dir`/`File` type theoretically allows us to say "this path ought to point to a file", there is literally zero guarantee that it will hold true at runtime. So this basically gives a false feeling of a type-safe file distinction. * it's imprecise about Dir vs File distinction, which makes it even worse, because a directory is also a file (just not a regular file). Add symlinks to that and the confusion is complete. * it makes the API oddly complicated for use cases where we basically don't care (yet) whether something turns out to be a directory or not Still, it comes also with a few perks: * it simplifies some functions, because they now have guarantees whether a path ends in a trailing path separator or not * it may be safer for interaction with other library functions, which behave differently depending on a trailing path separator (like probably shelly) Not limited to, but also in order to fix my remarks without breaking any benefits, I did: * rename the `Dir`/`File` types to `TPS`/`NoTPS`, so it's clear we are only giving information about trailing path separators and not actual file types we don't know about yet * add a `MaybeTPS` type, which does not mess with trailing path separators and also gives no guarantees about them... then added `toNoTPS` and `toTPS` to allow type-safe conversion * make some functions accept more general types, so we don't unnecessarily force paths with trailing separators for `(</>)` for example... instead these functions now examine the paths to still have correct behavior. This is really minor overhead. You might say now "but then I can append filepath to filepath". Well, as I said... we don't know whether it's a "filepath" at all. * merge `filename` and `dirname` into `basename` and make `parent` be `dirname`, so the function names match the name of the POSIX ones, which do (almost) the same... * fix a bug in `basename` (formerly `dirname`) which broke the type guarantees * add a pattern synonym for easier pattern matching without exporting the internal Path constructor
2016-03-08 21:53:42 +00:00
# HPath
2015-05-08 12:35:05 +00:00
Support for well-typed paths in Haskell.
## Motivation
Fork chrisdone's path library I wasn't happy with the way it dealt with Dir vs File things. In his version of the library, a `Path b Dir` always ends with a trailing path separator and `Path b File` never ends with a trailing path separator. IMO, it is nonsensical to make a Dir vs File distinction on path level, although it first seems nice. Some of the reasons are: * a path is just that: a path. It is completely disconnected from IO level and even if a `Dir`/`File` type theoretically allows us to say "this path ought to point to a file", there is literally zero guarantee that it will hold true at runtime. So this basically gives a false feeling of a type-safe file distinction. * it's imprecise about Dir vs File distinction, which makes it even worse, because a directory is also a file (just not a regular file). Add symlinks to that and the confusion is complete. * it makes the API oddly complicated for use cases where we basically don't care (yet) whether something turns out to be a directory or not Still, it comes also with a few perks: * it simplifies some functions, because they now have guarantees whether a path ends in a trailing path separator or not * it may be safer for interaction with other library functions, which behave differently depending on a trailing path separator (like probably shelly) Not limited to, but also in order to fix my remarks without breaking any benefits, I did: * rename the `Dir`/`File` types to `TPS`/`NoTPS`, so it's clear we are only giving information about trailing path separators and not actual file types we don't know about yet * add a `MaybeTPS` type, which does not mess with trailing path separators and also gives no guarantees about them... then added `toNoTPS` and `toTPS` to allow type-safe conversion * make some functions accept more general types, so we don't unnecessarily force paths with trailing separators for `(</>)` for example... instead these functions now examine the paths to still have correct behavior. This is really minor overhead. You might say now "but then I can append filepath to filepath". Well, as I said... we don't know whether it's a "filepath" at all. * merge `filename` and `dirname` into `basename` and make `parent` be `dirname`, so the function names match the name of the POSIX ones, which do (almost) the same... * fix a bug in `basename` (formerly `dirname`) which broke the type guarantees * add a pattern synonym for easier pattern matching without exporting the internal Path constructor
2016-03-08 21:53:42 +00:00
The motivation came during development of
[hsfm](https://github.com/hasufell/hsfm)
which has a pretty strict File type, but lacks a strict Path type, e.g.
for user input.
The library that came closest to my needs was
[path](https://github.com/chrisdone/path),
but the API turned out to be oddly complicated for my use case, so I
decided to fork it.
## Differences to 'path'
2016-04-16 16:17:44 +00:00
* doesn't attempt to fake IO-related types into the path, so whether a path points to a file or directory is up to your IO-code to decide... this should be a library that is used _with_ a proper IO File Type
* trailing path separators will be preserved if they exist, no messing with that
* uses safe ByteString for filepaths under the hood instead of unsafe String
* fixes broken [dirname](https://github.com/chrisdone/path/issues/18)
* renames dirname/filename to basename/dirname to match the POSIX shell functions
* introduces a new `Path Fn` for safe filename guarantees and a `RelC` class
* allows pattern matching via unidirectional PatternSynonym
* uses simple doctest for testing
* allows `~/` as relative path, because on posix level `~` is just a regular filename that does _NOT_ point to `$HOME`
* remove TH, it sucks