An un-zonked type can have type variables which are mutable references filled in during unification (and this mutability is heavily used by the type checker to increase performance). Zonking traverses a type and replaces all mutable references with the type that they dereference to; thus, the resulting structure is immutable and requires no dereferencing to … Read more
Are you looking for the -ddump-splices flag to the compiler?
You’ll need to use extra-lib-dirs and extra-libraries in the executable section of your .cabal file like so: name: MyApp version: 0.1.0.0 synopsis: homepage: author: simon.bourne category: build-type: Simple cabal-version: >=1.10 library exposed-modules: HelloWorld build-depends: base >= 4.7 && < 5 hs-source-dirs: src default-language: Haskell2010 executable MyApp main-is: Main.hs extra-lib-dirs: lib extra-libraries: helloWorld build-depends: base >= … Read more
You touch so many interesting points in your question, so I am afraid this is going to be a long answer 🙂 Kind of (->) The kind of (->) is * -> * -> *, if we disregard the boxity GHC inserts. But there is no circularity going on, the ->s in the kind of … Read more
Let me list my two biggest problems with compiling to C. If this is a problem for your language depends on what kind of features you have. Garbage collection When you have garbage collection you may have to interrupt regular execution at just about any point in the program, and at this point you need … Read more
There are three differences between using INLINABLE and not using a pragma at all: Without INLINABLE, the definition that goes in the interface file is the code after optimisation, whereas with INLINABLE, it is the code you wrote (more or less). In particular, without INLINABLE, GHC might inline other functions into the function’s definition. Without … Read more
Without FlexibleContexts all typeclass constraints on function definitions must have type variables. For example: add :: Num a => a -> a -> a add = (+) Where a is the type variable. With FlexibleContexts enabled you can have any type inside a typeclass. intAdd :: Num Int => Int -> Int -> Int intAdd … Read more
The majority of the technical information about the architecture and approach of the GHC system is in their wiki. I’ll link to the key pieces, and some related papers that people may not know about. What typical optimizations are applied? The key paper on this is: A transformation-based optimiser for Haskell, SL Peyton Jones and … Read more
Lists have no special operational treatment in Haskell. They are defined just like: data List a = Nil | Cons a (List a) Just with some special notation: [a] for List a, [] for Nil and (:) for Cons. If you defined the same and redefined all the operations, you would get the exact same … Read more
From the blog post @Lambdageek linked, the GHC Commentary and the GHC User’s Guide I piece together the following: GHC tries to prevent reevaluating thunks, but because true locking between threads is expensive, and thunks are usually pure and so harmless to reevaluate, it normally does so in a sloppy manner, with a small chance … Read more