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digitalmars.D - Java type annotations, multi-precision

reply "bearophile" <bearophileHUGS lycos.com> writes:
Two unrelated things found recently on Reddit:

In Java 8 they have added type annotations:
http://www.mscharhag.com/2014/02/java-8-type-annotations.html


This shows how a C-like language lacks some essential parts to 
use well the CPUs (both x86 and to ARM) to implement range 
integrals or multi-word integrals efficiently without using asm:
http://accu.org/index.php/journals/1849

Bye,
bearophile
Feb 09 2014
next sibling parent reply "Francesco Cattoglio" <francesco.cattoglio gmail.com> writes:
On Sunday, 9 February 2014 at 15:38:24 UTC, bearophile wrote:

 Two unrelated things found recently on Reddit:

 In Java 8 they have added type annotations:
 http://www.mscharhag.com/2014/02/java-8-type-annotations.html


Wow, they are totally coping! :P Jokes aside, now I wonder: what 
language introduced type anotation first?
Feb 09 2014
next sibling parent "Ola Fosheim =?UTF-8?B?R3LDuHN0YWQi?= writes:
On Sunday, 9 February 2014 at 16:23:50 UTC, Francesco Cattoglio 
wrote:

 Wow, they are totally coping! :P Jokes aside, now I wonder: 
 what language introduced type anotation first?


Probably some CASE tool 20-30 years ago or so.
Feb 09 2014
prev sibling next sibling parent Paulo Pinto <pjmlp progtools.org> writes:
Am 09.02.2014 17:23, schrieb Francesco Cattoglio:

 On Sunday, 9 February 2014 at 15:38:24 UTC, bearophile wrote:

 Two unrelated things found recently on Reddit:

 In Java 8 they have added type annotations:
 http://www.mscharhag.com/2014/02/java-8-type-annotations.html


 Wow, they are totally coping! :P Jokes aside, now I wonder: what
 language introduced type anotation first?


.NET did it before Java.

Along the way Python got them too.

Common Lisp and Dylan had them before the former.

--
Paulo
Feb 09 2014
prev sibling parent reply "bearophile" <bearophileHUGS lycos.com> writes:
Francesco Cattoglio:


 Wow, they are totally coping! :P


What's interesting is not just that Java has type annotations, 
but the details of this feature. That article show many details.

Bye,
bearophile
Feb 09 2014
parent reply "Meta" <jared771 gmail.com> writes:
On Sunday, 9 February 2014 at 17:55:50 UTC, bearophile wrote:

 Francesco Cattoglio:


 Wow, they are totally coping! :P


 What's interesting is not just that Java has type annotations, 
 but the details of this feature. That article show many details.

 Bye,
 bearophile


I don't think he mentioned it in the first article, but are these 
annotations checked at runtime or compile time? For example, 
 NonNegative.
Feb 09 2014
parent Timon Gehr <timon.gehr gmx.ch> writes:
On 02/09/2014 07:25 PM, Meta wrote:

 On Sunday, 9 February 2014 at 17:55:50 UTC, bearophile wrote:

 Francesco Cattoglio:


 Wow, they are totally coping! :P


 What's interesting is not just that Java has type annotations, but the
 details of this feature. That article show many details.

 Bye,
 bearophile


 I don't think he mentioned it in the first article, but are these
 annotations checked at runtime or compile time? For example,  NonNegative.


Java does not assign any interesting semantics to those annotations. 
They however can be used together with tools/compiler plugins. Eg. one 
could use tools that recognize  NonNegative in order to add runtime 
checks or apply static analysis, or some combination of the two.
Feb 09 2014
prev sibling next sibling parent Paulo Pinto <pjmlp progtools.org> writes:
Am 09.02.2014 16:38, schrieb bearophile:

 Two unrelated things found recently on Reddit:

 In Java 8 they have added type annotations:
 http://www.mscharhag.com/2014/02/java-8-type-annotations.html


 This shows how a C-like language lacks some essential parts to use well
 the CPUs (both x86 and to ARM) to implement range integrals or
 multi-word integrals efficiently without using asm:
 http://accu.org/index.php/journals/1849

 Bye,
 bearophile


I tend to have some fun pointing out on online forums like HN, that 
despite common belief, it is 100% ANSI/ISO compliant to have C and C++ 
compilers that don't expose inline assembly, cpu intrisics and that 
those languages no longer map directly to modern CPUs architectures like 
they did in the 70's.

--
Paulo
Feb 09 2014
prev sibling parent reply Walter Bright <newshound2 digitalmars.com> writes:
On 2/9/2014 7:38 AM, bearophile wrote:

 This shows how a C-like language lacks some essential parts to use well the
CPUs
 (both x86 and to ARM) to implement range integrals or multi-word integrals
 efficiently without using asm:
 http://accu.org/index.php/journals/1849


Much like how ROR and ROL is efficiently handled in compilers by having the 
compiler recognize the equivalent expression, I think the best way to handle 
these issues is by having the compiler recognize the multi-precision 
expressions, and rewrite it internally into the optimal asm.
Feb 09 2014
parent "bearophile" <bearophileHUGS lycos.com> writes:
Walter Bright:


 Much like how ROR and ROL is efficiently handled in compilers 
 by having the compiler recognize the equivalent expression, I 
 think the best way to handle these issues is by having the 
 compiler recognize the multi-precision expressions, and rewrite 
 it internally into the optimal asm.


See:
https://d.puremagic.com/issues/show_bug.cgi?id=6829

My opinions:
- It's a fragile pattern recognition. In D.learn and elsewhere I 
have seen people write the rot/rol in a way that DMD is not able 
to recognize.
- It's not portable, because there is no guarantee that other 
present or future compilers will perform that optimization. See 
that issue 6829 thread for problems with LLVM.
- Generally it's nice to have a language that offers higher level 
operations to the programmer, making coding simpler. But in this 
case calling a function as rol/ror is very easy for the 
programmer, it is not a burden at all. Replacing it with a 
pattern to be written carefully is not a gain for the programmer. 
And it helps the person that later reads the code at a bit higher 
level (and currently Phobos doesn't have such ror/rol functions, 
so they need to be written in user code).

Here I have suggested something different:
https://d.puremagic.com/issues/show_bug.cgi?id=9850

Bye,
bearophile
Feb 09 2014