First off, * is not a wildcard! It’s also typically pronounced “star.” Bleeding edge note: There is as of Feb. 2015 a proposal to simplify GHC’s subkind system (in 7.12 or later). That page contains a good discussion of the GHC 7.8/7.10 story. Looking forward, GHC may drop the distinction between types and kinds, with … Read more
With the development branch of GHC (anyone know exactly which version this was added in?): $ ghc -o hello hello.hs $ strip -p –strip-unneeded –remove-section=.comment -o hello-small hello $ du hello hello-small 700 hello 476 hello-small Add the -dynamic flag for a dynamically linked RTS: $ ghc -dynamic -o hello hello.hs $ strip -p –strip-unneeded … Read more
It’s a little bit of overkill, but one solution is to combine OverloadedStrings and RebindableSyntax. The RebindableSyntax extension causes all the implicit function calls that Haskell syntax uses to refer to whatever functions are in scope; for instance, integer literals use any fromIntegral, not necessarily Prelude.fromIntegral. As a side effect, Prelude is no longer implicitly … Read more
I guess I’m one of the few people who have first hand experience of why it was hard, since I implemented it in hbc when there was no prior art. So what was clear from the Wadler&Blott paper was that type checking was an extension of Hindley-Milner type checking and that at runtime you should … Read more
I’ve gone through the GHC docs a bit, and there doesn’t seem to be a built-in way to remove the temporary files automatically — after all, GHC needs those intermediate files to build the final executable, and their presence speeds up overall compilation when GHC knows it doesn’t have to recompile a module. However, you … Read more
It is possible to create working shared libraries on 64-bit OS X, with the latest Haskell Platform release (2012.4 64bit) The invocation line works for me: ghc -O2 –make \ -no-hs-main -optl ‘-shared’ -optc ‘-DMODULE=Test’ \ -o libTest.so Test.hs module_init.c module_init.c should be something like: #define CAT(a,b) XCAT(a,b) #define XCAT(a,b) a ## b #define STR(a) … Read more
This is because ghci disables buffering, while a program compiled with ghc has line buffering by default. You can see this by running this: import System.IO main = print =<< hGetBuffering stdout In ghci you see NoBuffering while with runghc you get LineBuffering. Since the newline character doesn’t print until after the user input, the … Read more
To find which version my stack is using, I ran $ stack ghc — –version and got $ stack ghc — –version The Glorious Glasgow Haskell Compilation System, version 8.0.2
Alas, there is no magic in the tuples. Here’s the implementation GHC uses, and to give you some idea of what’s going on here’s the source for the last definition: data (,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,) a b c d e f g h i j k l m n o p q r s t u v w … Read more
In general, fusion refers to transformations whose purpose is to get rid of intermediate data structures. You fuse function calls that result in wasteful memory allocations into something more efficient. This is actually IMO one of the biggest applications of Haskell being pure. And you pretty much don’t need to do anything to get it, … Read more