Re: lookuptable
On 4/22/20 5:21 PM, Sebastiaan Koppe wrote: On Wednesday, 22 April 2020 at 20:27:12 UTC, Steven Schveighoffer wrote: Just wanted to throw this out there on a slow day. I wrote this little utility to generate static lookup tables, because using an AA is too expensive for something like e.g. looking up database row data by column name. It's very crude, but very short and sweet. Hopefully people find a use for it. Let me know if you have any requests or find any bugs on github. https://code.dlang.org/packages/lookuptable Nice. For the indexLookup you can also use https://github.com/skoppe/perfect-hash Hm... thanks for the suggestion. I'm not sure if it fits here, as the point is to avoid runtime cost and GC allocation, not make lookups uber-fast. These are meant to be short-lived things. My main target was e.g. mysql-native has an "asAA" function which generates an AA with keys being the column names. This is kind of crappy, because if you do that for each row, then you are generating and throwing away a LOT of data. But if you generate the lookup index once per sequence, and you reuse that, you have much more efficiency, and are only generating one array. Possibly if I can figure out a good API, you could do it with malloc/free instead of using GC, but I'm happy with it right now anyway. -Steve
Re: lookuptable
On Wednesday, 22 April 2020 at 21:21:31 UTC, Sebastiaan Koppe wrote: For the indexLookup you can also use https://github.com/skoppe/perfect-hash That is not quite true, only for strings.
Re: lookuptable
On Wednesday, 22 April 2020 at 20:27:12 UTC, Steven Schveighoffer wrote: Just wanted to throw this out there on a slow day. I wrote this little utility to generate static lookup tables, because using an AA is too expensive for something like e.g. looking up database row data by column name. It's very crude, but very short and sweet. Hopefully people find a use for it. Let me know if you have any requests or find any bugs on github. https://code.dlang.org/packages/lookuptable -Steve Nice. For the indexLookup you can also use https://github.com/skoppe/perfect-hash
lookuptable
Just wanted to throw this out there on a slow day. I wrote this little utility to generate static lookup tables, because using an AA is too expensive for something like e.g. looking up database row data by column name. It's very crude, but very short and sweet. Hopefully people find a use for it. Let me know if you have any requests or find any bugs on github. https://code.dlang.org/packages/lookuptable -Steve
Re: describe-d: an introspection library
On Wednesday, 22 April 2020 at 17:32:33 UTC, Stefan Koch wrote: It's going to be part of the compiler. You can look at the ... expression DIP. which Manu posted in General, for taste of where my stuff is going. I think I see the point - I am familiar with C++ variadic templates. Yes, speeding up `staticMap`, and often eliminating the need to use it, will hugely benefit meta-programming. However, that will not solve the problem of unnecessary instantiations that my example above demonstrates (it has a bug btw, the parameters should have been wrapped in a bolts.meta.AliasPack, but it doesn't alter the spirit). Thank you for the `-vcg-ast` switch! It looks like I am going to use it a lot. I am rewriting my system to express the accessors in terms of free functions taking meta-objects, instead of meta-objects containing properties. I have a hunch that that will curb instantiation, compile time and .o size.
Re: describe-d: an introspection library
On Wednesday, 22 April 2020 at 17:27:48 UTC, Jean-Louis Leroy wrote: On Wednesday, 22 April 2020 at 17:16:28 UTC, Stefan Koch wrote: I am working on a much more powerful and efficient meta programming system. Great! Is it going to be in a library, or part of the compiler? Can we get a preview somewhere? It's going to be part of the compiler. You can look at the ... expression DIP. which Manu posted in General, for taste of where my stuff is going. Basically I will give CTFE the ability to modify type-lists directly.
Re: describe-d: an introspection library
On Wednesday, 22 April 2020 at 17:16:28 UTC, Stefan Koch wrote: I am working on a much more powerful and efficient meta programming system. Great! Is it going to be in a library, or part of the compiler? Can we get a preview somewhere?
Re: describe-d: an introspection library
On Wednesday, 22 April 2020 at 13:32:03 UTC, Jean-Louis Leroy wrote: I tried compiling my example with `dmd -vcg-ast -c tmt.d` and I did got neither an AST nor an error, and the option is not in `dmd -h`, where can I read about it? -vcg-ast is a debugging tool I original built to fix an bug in the inliner. when you through the switch a new file of the form "soucefilename.d.cg" should get written out for every sourcefile in the same directory that the source file is in. As for your other point. I am working on a much more powerful and efficient meta programming system. It's no where near done. So I will not commit to any release date ... I've learned my lesson.
Re: describe-d: an introspection library
On Wednesday, 22 April 2020 at 05:20:18 UTC, Stefan Koch wrote:
On Tuesday, 21 April 2020 at 14:43:04 UTC, Jean-Louis Leroy
wrote:
I wonder if templates are lazily expanded. I haven't looked at
the compiler's code, my guess is: maybe not.
If the template gets used it gets instantiated (and cached).
I did not word my question precisely, I meant: is it instantiated
in its *entirety*.
Consider:
import std.meta;
template Function(Attributes...)
{
enum isPure = Attributes[0];
enum isNogc = Attributes[1];
alias parameters = Attributes[2];
}
template Parameter(int i)
{
// static assert(false);
}
template reflectFunction(alias Fun)
{
alias reflectFunction = Function!(
true, true, staticMap!(Parameter, 1, 2, 3));
}
void foo();
pragma(msg, reflectFunction!(foo).isPure);
Is `Parameter` instantiated in this example? If I uncomment the
assert, it fires. This is what gives me the impression that more
is instantiated than is really used. And that is probably why
reflecting runtime entities as template meta-objects with
properties for all aspects of them is slow.
I am way of my field of competence here, but I have the
impression that speeding this up would not require a change in
the language (unless it is stated that templates are greedily
expanded, and common idioms rely on this).
you can use the -vcg-ast switch to look at how your souce code
looks "expandend".
I tried compiling my example with `dmd -vcg-ast -c tmt.d` and I
did got neither an AST nor an error, and the option is not in
`dmd -h`, where can I read about it?
They already gained traction, unfortunately.
Well...Two things. I ended up developing this approach because I
needed to copy function attributes, UDAs, function parameter
storage classes and UDAs to a generated function. If the
language, or Phobos, provided me a more direct way, trust me, I
would have used it. For example, storage classes are not part of
a parameter's type. OK. Now you can use `Parameter!F[0]` to
declare a parameter in a new function (great!), but you cannot
say `__traits(getStorageClasses, F)[0] Parameter!F[0]`.
Also, one of D's selling points is that it does templates and
meta-programming better. It's only natural that people use these
features then (note that in C++, sorry for mentioning it, in my
example Parameter would *not* be instantiated).
Discussion Thread: DIP 1033--Implicit Conversion of Expressions to Delegates--Community Review Round 1 Begins
The first round of Community Review of DIP 1033, "Implicit Conversion of Expressions to Delegates", has begun. Feedback Thread: https://forum.dlang.org/post/nxahrsukobybkezib...@forum.dlang.org Discussion Thread: https://forum.dlang.org/post/ecxdylguqkhtmdoml...@forum.dlang.org
