Changes between Version 4 and Version 5 of Status/Oct10


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Timestamp:
Oct 22, 2010 11:04:19 PM (5 years ago)
Author:
simonpj
Comment:

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  • Status/Oct10

    v4 v5  
    33GHC is humming along.  We are currently deep into the release cycle for GHC 7.0.  We have finally bumped the major version number, becuase GHC 7.0 has quite a bit of new stuff 
    44 
    5  * As long promised, Simon PJ and Dimitrios have spent a good chunk of the summer doing a complete rewrite of the constraint solver in the type inference engine.  Because of GHC's myriad type-system extensions, especially GADTs and type famlies, the old engine had begun to resemble the final stages of a game of Jenga.  It was a delicately-balanced pile of blocks that lived in constant danger of complete collapse, and had become extremely different to modify (or even to understand).  The new inference engine is much more modular and robust; it is described in detail in our paper [[http://haskell.org/haskellwiki/Simonpj/Talk:OutsideIn OutsideIn]].  A blog post describes some consequential changes to let generalisation [LetGen]. 
     5 * As long promised, Simon PJ and Dimitrios have spent a good chunk of the summer doing a complete rewrite of the constraint solver in the type inference engine.  Because of GHC's myriad type-system extensions, especially GADTs and type famlies, the old engine had begun to resemble the final stages of a game of Jenga.  It was a delicately-balanced pile of blocks that lived in constant danger of complete collapse, and had become extremely different to modify (or even to understand).  The new inference engine is much more modular and robust; it is described in detail in our paper [[http://haskell.org/haskellwiki/Simonpj/Talk:OutsideIn OutsideIn]].  A blog post describes some consequential changes to let generalisation [!LetGen]. 
    66 
    77 As a result we have closed dozens of open type inference bugs, especially related to GADTs and type families. 
     
    4242Here's a selection that we know about. 
    4343 
    44  * Pedro Magalhaes is implementing the "derivable type classes" mechanism described in his 2010 Hsakell Symposium paper [Derivable].  I plan for this to replace GHC's current derivable-type-class mechanism, which has a poor power-to-weight ratio and is little used. 
     44 * Pedro Magalhaes is implementing the '''derivable type classes''' mechanism described in his 2010 Hsakell Symposium paper [Derivable].  I plan for this to replace GHC's current derivable-type-class mechanism, which has a poor power-to-weight ratio and is little used. 
    4545 
    46  * Stephanie Weirich and Steve Zdancewic had a great sabbatical year at Cambridge.  One of the things we worked on, with Brent Yorgey who came as an intern, was to close the embarrassing hole in the type system concerning "newtype deriving" (see Trac bug #1496).  I have delayed fixing until I could figure out a Decent Solution, but now we know; see our 2011 POPL paper [Newtype].  Brent is working on some infrastructal changes to GHC's Core language, and then we'll be ready to tackle the main issue. 
     46 * Stephanie Weirich and Steve Zdancewic had a great sabbatical year at Cambridge.  One of the things we worked on, with Brent Yorgey who came as an intern, was to close the embarrassing hole in the type system concerning '''newtype deriving''' (see Trac bug #1496).  I have delayed fixing until I could figure out a Decent Solution, but now we know; see our 2011 POPL paper [Newtype].  Brent is working on some infrastructal changes to GHC's Core language, and then we'll be ready to tackle the main issue. 
    4747 
    48  * Next after that is a mechanism for promotimg types to become kinds, and data constructors to become types, so that you can do ''typed'' functional programming at the type level.  Conor !McBride's SHE prototype is the inspiration here [SHE].  Currently it is, embarrassingly, essentially untyped.   
     48 * Next after that is a mechanism for '''promotimg types to become kinds''', and data constructors to become types, so that you can do ''typed'' functional programming at the type level.  Conor !McBride's SHE prototype is the inspiration here [SHE].  Currently it is, embarrassingly, essentially untyped.   
    4949 
    50  * Template Haskell seems to be increasingly widely used.  Simon PJ has written a proposal for a raft of improvements, which we plan to implement in the new year [TemplateHaskell]. 
     50 * '''Template Haskell''' seems to be increasingly widely used.  Simon PJ has written a proposal for a raft of improvements, which we plan to implement in the new year [!TemplateHaskell]. 
    5151 
    52  * Iavor Diatchki plans to add numeric types, so that you can have a type like `Bus 8`, and do simple arithmetic at the type level.  You can encode this stuff, but it's easier to use and more powerful to do it directly. 
     52 * Iavor Diatchki plans to add '''numeric types''', so that you can have a type like `Bus 8`, and do simple arithmetic at the type level.  You can encode this stuff, but it's easier to use and more powerful to do it directly. 
    5353 
    54  * David Mazieres at Stanford wants to implement "Safe Haskell", a flag for GHC that will guarantee that your program does not use `unsafePerformIO`, foreign calls, RULES, and other stuff stuff.  This is part of his projet to ... '''David pls fill in'''. 
     54 * David Mazieres at Stanford wants to implement '''Safe Haskell''', a flag for GHC that will guarantee that your program does not use `unsafePerformIO`, foreign calls, RULES, and other stuff stuff.  This is part of his projet to ... '''David pls fill in'''. 
    5555 
    5656== Packges and the runtime system == 
     
    8080 * [Derivable] "A generic deriving mechanism for Haskell", Magalhães, Dijkstra, Jeuring and Löh, Haskell Symposium 2010, www.dreixel.net/research/pdf/gdmh_nocolor.pdf. 
    8181 
    82  * [LetGen] "Let generalisation in GHC 7.0", Peyton Jones, blog post Sept 2010, http://hackage.haskell.org/trac/ghc/blog/LetGeneralisationInGhc7 
     82 * [!LetGen] "Let generalisation in GHC 7.0", Peyton Jones, blog post Sept 2010, http://hackage.haskell.org/trac/ghc/blog/LetGeneralisationInGhc7 
    8383 * [Newtype] "Generative Type Abstraction and Type-level Computation", Weirich, Zdancewic, Vytiniotis, and Peyton Jones, POPL 2010, http://www.cis.upenn.edu/~sweirich/newtypes.pdf 
    8484 
     
    8787 * [SHE] The Strathclyde Haskell Enhancement, Conor McBride, 2010, http://personal.cis.strath.ac.uk/~conor/pub/she/ 
    8888 
    89  * [TemplateHaskell] New directions for Template Haskell, Peyton Jones, blog post October 2010, http://hackage.haskell.org/trac/ghc/blog/Template%20Haskell%20Proposal 
     89 * [!TemplateHaskell] New directions for Template Haskell, Peyton Jones, blog post October 2010, http://hackage.haskell.org/trac/ghc/blog/Template%20Haskell%20Proposal