[racket-dev] Generics updates

From: Carl Eastlund (cce at ccs.neu.edu)
Date: Thu Jul 25 13:58:29 EDT 2013

After some fixes, mostly to contracts and documentation, I've pushed the
new generics and set features to the master branch.

Carl Eastlund

On Tue, Jul 23, 2013 at 11:37 AM, Carl Eastlund <cce at ccs.neu.edu> wrote:

> My work on adding gen:set, and related changes to define-generics and
> gen:dict, is ready for review and (hopefully) to push to the master
> branch.  The branch moved in the process of cleaning things up, it's now at:
>   https://github.com/carl-eastlund/racket/tree/generics-from-scratch
> (The "from scratch" just refers to the process of rebuilding the git
> history, I didn't go out of my way to rewrite anything in the code base
> from scratch, although in some places a lot of code did move around.)
> What's new in the branch:
> - Generics now support a few new options
>   - #:fallbacks specifies fallback method implementations for instances
> with no implementation
>   - #:fast-defaults specifies instances on a "fast path", useful for
> built-in types
>   - #:defined-predicate gives a more intuitive and efficient interface
> than #:defined-table
>   - #:derive-property allows generics to piggy-back on existing struct
> properties
> - Sets are now a generic datatype through gen:set
>   - lists are now sets
>   - the built-in set types are now documented as "hash sets"
>   - there are mutable and weak hash sets
>   - you can define new set types quickly with define-custom-set-types
>   - most set operations are now methods with fallbacks
>   - sets now support -copy and -clear operations, plus mutating [!]
> versions of operations
> - Dictionaries have a few changes
>   - new macro define-custom-hash-types [*]
>   - most dict operations are now methods with fallbacks
>   - dicts now support -copy, -clear, -clear!, and -empty? operations
> I've run some benchmarks and performance of the various generic operations
> are comparable to the current HEAD, so there should be no major performance
> changes with this patch.
> [*] I've added define-custom-hash-types and define-custom-set-types rather
> than just adding make-custom-set akin to make-custom-hash because
> make-custom-hash is hard to use.  The documented behavior -- that any
> custom hash is equal to any other created with the same bindings and
> predicates / hash functions -- was never true and can be expensive or at
> least tricky to implement.  It seemed more sensible to just remove the
> erroneous documentation on make-custom-hash, and add the definition form to
> create constructors for new, explicitly-compatible dict and set types.
> Both definition forms bind predicates and constructors for new (set or
> dict) types with immutable, mutable, and weak variants that inter-operate.
> If there are no serious issues brought up in the next day or two, I'll
> push it to the development branch, since our current release process isn't
> following HEAD.
> Carl Eastlund
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