On 7/30/2019 12:59 PM, Atlas Atlas wrote:
вторник, 30 июля 2019 г., 4:40:40 UTC+3 пользователь Sam
Tobin-Hochstadt написал:
I'm not exactly sure what you're asking for here -- the CL type
system
works very differently -- but local annotation is certainly possible
in Typed Racket. The `ann` form allows you to annotate any expression
at all, ie `(ann 17 Integer)`.
Sam
The idea is you don't need to write this annotations. You can if you want.
In typed racket it is demand.
This became problem with untyped libraries, especially when they
produce complex data. Or have complex macros.
Sometimes this catches you with iterations.
Simple example
(define (test-f a)
(string-append a " okay"))
Typed-racket produces error: /"Type Checker: type mismatch expected:
String given: Any"/ when type of _a_ can easily be inferred.
Solution is to infer type, or leave code untyped in some default way.
Another problem
require/typed - wraps code with contracts what have negative impact on
performance, sometimes really bad one.
I just find current typed\racket condition unpractical.
I need for example to write my own untyped lib for using another
untyped lib to simplify interfaces and make impact on performance more
acceptable.
It seams what I am asking for here is unsound typing.
Latent typing ... what #lang Racket, Scheme and Lisp, etc. provide ...
is not "unsound": the data types are known and enforced, but the
enforcement is at run time, and the result is that there are code size
(type tests), data size (type tags or other metadata), and performance
hits due to them. The whole point of type declarations, type
inferencing and so forth is to have the types known at compile time for
sooner error diagnostics, and to increase performance by eliminating
unneeded runtime testing.
Another option is to force! typed racket on all levels in all libs.
I am not so big expert in theory of language design..
There is some paper I found
www.ccis.northeastern.edu/home/types/publications/gradual-dead/pre-treatment.pdf
<http://www.ccis.northeastern.edu/home/types/publications/gradual-dead/pre-treatment.pdf>
on this matter, called "Is Sound Gradual Typing Dead?" from
Northeastern University, it highlights some of the problems in more
scientific way.
George
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