Implementing a minimal version of haskell-servant
Recently, there was a question on Stack Overflow on how Servant actually works. Others were quick to suggest the Servant paper as a thorough explanation of the approach and the implementation. As a co-author, I’m obviously happy if the paper is being read, but it’s also 12 pages long in two-column ACM style. And while it explains the implementation, it does not necessarily make it easier to start
Dependently typed servers in Servant
Suppose we have a webserver that can perform different kinds of operations on different kinds of values. Perhaps it can reverse or capitalize strings, and increment or negate integers: # curl http://localhost:8081/example/reverse elpmaxe # curl http://localhost:8081/example/caps EXAMPLE # curl http://localhost:8081/1234/inc 1235 # curl http://localhost:8081/1234/neg -1234 Moreover, it can echo bac
OverloadedRecordFields revived
Way back in the summer of 2013, with support from the Google Summer of Code programme, I implemented a GHC extension called OverloadedRecordFields to address the oft-stated desire to improve Haskell’s record system. This didn’t get merged into GHC HEAD at the time, because the implementation cost outweighed the benefits. Now, however, I’m happy to report that Well-Typed are sponsoring the work req
Overloaded record fields for GHC - Well-Typed - The Haskell Consultants
TL;DR: GHC HEAD (but not GHC 7.8) will soon support OverloadedRecordFields, an extension to permit datatypes to reuse field labels and even turn them into lenses. IntroductionThe Haskell records system is a frequent source of frustration to Haskell programmers working on large projects. On the face of it, it is simple: a datatype such as data Person = Person { id :: Int, name :: String } gives ris
How we might abolish Cabal Hell, part 1
At ICFP a few weeks ago a hot topic in the corridors and in a couple talks was the issues surrounding packaging and “Cabal Hell.” Fortunately we were not just discussing problems but solutions. Indeed I think we have a pretty good understanding now of where we want to be, and several solutions are in development or have reasonably clear designs in peoples’ heads. I want to explain what’s going on
Quasi-quoting DSLs for free
Suppose you are writing a compiler for some programming language or DSL. If you are doing source to source transformations in your compiler, perhaps as part of an optimization pass, you will need to construct and deconstruct bits of abstract syntax. It would be very convenient if we could write that abstract syntax using the syntax of your language. In this blog post we show how you can reuse your
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http://www.well-typed.com/blog/aux/files/overloaded-record-fields.pdf