Add Result type and operators

07 May 2015 ❘ FootlessParser  

This is part of a series on FootlessParser, a parser combinator written in Swift.

Add Runes and LlamaKit using Carthage

https://github.com/kareman/FootlessParser/commit/6142452334dae45a5aae65e0f54264f1ea3f533d

Footlessparser is using operators for map ( <^> ), flatmap/bind ( »- ) and apply ( <*> ). Luckily the Runes framework has already defined these, and implemented them for optionals and arrays.

Each parse returns a Result, which has either a tuple containing the output and the remaining unparsed part of the input, or an error description if parsing fails. The Result enum is in the Llamakit framework, later replaced by antitypical/Result.

Add Runes+Result.swift

https://github.com/kareman/FootlessParser/commit/c49709d9bb17291fac6b82a0fe136d6d10e1bd9f

To implement the operators mentioned above for parsers it is very helpful to first implement them for what parsers return, i.e. Result. Gordon Fontenot did just that in this pull request to Runes. It was never merged, so it’s included here.

Rename Runes+Result.swift to Result+Operators.swift

https://github.com/kareman/FootlessParser/commit/74230bb5148e827debf610c8f3c8259b8b4a77b9

I renamed the file later to make the name more descriptive and not so foreign for those who have not heard about the Runes framework.

Switch from LlamaKit/LlamaKit to antitypical/Result.

https://github.com/kareman/FootlessParser/commit/f527d9e0e8999479c4627dd4ffdd5871174b7edf

Later on the Llamakit project recommended switching to antitypical/Result. This lead to several changes:

• the success and failure functions for making a Result moved to the Result type and became static instead of global. Which is good, functions only involved with one type should be defined in that type.
• Result became a struct, not an enum. Which seems strange as it is either a success or a failure, never both. It was made back into an enum later.
• the Result framework brought with it the micro frameworks robrix/Box, robrix/Prelude and robrix/Either. Especially Prelude has some basic functional programming functionality that will come in handy.