Types are puzzles. A good Rustacean will make sure that the pieces fit to make the picture.<p>That's why in crates where I need to make sure certain functions are called in order, I use a Ticket<T>, where one function returns a Ticket<Func1Done> with the output and the other has to consume it as an input.<p>The typestate pattern is a specialization of making only valid states representable
I use Typestates and Newtypes extensively. The metric that shows Typestate and Newtypes are beneficial is: How many method calls or parameters can be called / used that compile but are not valid use cases. You want to minimise this number. I love having a type state where I can only make 1 or 2 method calls because the state enforces there are only a few parsing / validation / transition methods available. And there is only one valid way to supply the parameters, I cannot use the strings in the wrong location. I only wish we had named parameters like ObjC.
This was a talk at the FUNARCH workshop at this year’s ICFP.<p>Here’s the livestream: <a href="https://www.youtube.com/live/c0pw1iVs_Q0?is=hwm2xa4cZOcqF5tW" rel="nofollow">https://www.youtube.com/live/c0pw1iVs_Q0?is=hwm2xa4cZOcqF5tW</a><p>Well post the individual talks in the following days!
pdf: <a href="https://dl.acm.org/doi/pdf/10.1145/3830438.3830958" rel="nofollow">https://dl.acm.org/doi/pdf/10.1145/3830438.3830958</a>
Could someone compare this to ST in Idris?