[racket-dev] [plt] Push #27446: master branch updated

Nice, and thanks for the explanation. Just to make sure I get it: does 
this mean fully expanded TR modules are smaller?

Does it reduce the number of generated contracts?

On 09/08/2013 12:24 PM, Sam Tobin-Hochstadt wrote:
> Typed Racket has to expand into code that registers the type of each
> module-top-level identifier in the global environment so that other
> modules can find the types to typecheck with.  For example, this
> program:
>
> #lang typed/racket
> (provide x)
> (define: x : Integer 1)
>
> expands into (greatly simplified):
>
> #lang ...
> (#%provide x)
> (begin-for-syntax
>    (declare #'x Integer-rep))
> (define-values (x) 1)
>
> but what is `Integer-rep`?  It needs to be an expression that
> _constructs_ the internal Typed Racket representation of the `Integer`
> type. Previously, that looked something like this:
>
>      (make-Union (sort (list Negative-Fixnum-rep Positive-Fixnum-rep ...)))
>
> and so on and so forth for the components, all the way down to base
> types.  You can imagine how this gets quite large, especially for
> large types.
>
> However, this is wasteful, because every Typed Racket program, at type
> checking time, defines a constant that's the representation of the
> `Integer` type, right here [1]. So instead of serializing an
> expression that constructs the same thing as `-Int`, we can just
> *reference* `-Int` in the expanded code.  To make that possible, Typed
> Racket now builds a hash table [2] mapping types (really, their
> representations) to identifiers that denote those types. Then the
> serializer just consults this table [3].
>
> It turns out that base types (but no others) already used basically
> this mechanism, by storing the identifier *in* the type
> representation.  But that's now obsolete, and thus was removed in my
> subsequent commit.
>
> As a result, the type serialization is much smaller.
>
> [1] https://github.com/plt/racket/blob/master/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/numeric-tower.rkt#L107
> [2] https://github.com/plt/racket/blob/master/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/base-abbrev.rkt#L23
> [3] https://github.com/plt/racket/blob/master/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/env/init-envs.rkt#L51
>
> On Sat, Sep 7, 2013 at 3:20 PM, Neil Toronto <neil.toronto at gmail.com> wrote:
>> On 09/06/2013 04:14 PM, samth at racket-lang.org wrote:
>>>
>>> 56b372c Sam Tobin-Hochstadt <samth at racket-lang.org> 2013-09-06 14:22
>>> :
>>> | Remember types that are defined, and use them in serialization.
>>> |
>>> | This extends a facility already available for base types,
>>> | making that facility no longer strictly needed.
>>> |
>>> | Shrinks the zo size for the `math` package by almost 1MB.
>>> :
>>>     M .../typed-racket/env/init-envs.rkt                |   1 +
>>>     M .../typed-racket/typecheck/def-export.rkt         |   7 +-
>>>     M .../typed-racket/typecheck/tc-toplevel.rkt        |  31 +++---
>>>     M .../typed-racket/types/abbrev.rkt                 |  36 +++----
>>>     M .../typed-racket/types/base-abbrev.rkt            |  12 ++-
>>>     M .../typed-racket/types/numeric-tower.rkt          | 108
>>> +++++++++----------
>>
>>
>> Would you mind explaining this a little more? It sounds interesting, and the
>> commit almost has my name in it. :)
>>
>> Neil ⊥
>>