Re: emulate with

2019-06-01 Thread Simen Kjærås via Digitalmars-d-learn

On Friday, 31 May 2019 at 08:35:23 UTC, Simen Kjærås wrote:
With 1), 2) and 3) fixed, the code would look like this (only 
changed code included):


unittest {
with (Dispatcher.X) {
A(1);
A("a");
B(2);
C_Q(3);
}
}

struct Dispatcher {
struct opDispatch(string prefix, alias context = 
__CONTEXT__) {
static auto opDispatch(string name, Args...)(Args args) 
{

 return getMethod!(context, prefix~"_"~name)(args);
}
}
}


Actually, Dispatcher could look like this:

struct Dispatcher {
struct opDispatch(string prefix, alias context = __CONTEXT__) 
{
alias opDispatch(string name) = getMethod!(context, 
prefix~"_"~name);

}
}

--
  Simen


Re: emulate with

2019-05-31 Thread Amex via Digitalmars-d-learn

On Friday, 31 May 2019 at 08:35:23 UTC, Simen Kjærås wrote:

On Friday, 31 May 2019 at 07:17:22 UTC, Amex wrote:
What I'm talking about is that if A would be dispatched to, 
say, W!X where W handles the special dispatching by returning 
X_A rather than X.A.



I don't know if D can do this kinda stuff even though it would 
be rather simple as it would depend on with.


Of course D can! However, it's not really pretty, and I think I 
found a bug in the process.


This is my code that compiles and runs:

void X_A(int i) {}
void X_A(string s) {}
void X_B(int i) {}
void X_C_Q(int i) {}

unittest {
with (Dispatcher.X!({})) {
A(1);
A("a");
B(2);
C_Q(3);
}
}

template getMethod(alias x, string name) {
static if (__traits(hasMember, x, name)) {
alias getMethod = __traits(getMember, x, name);
} else static if (x.stringof[0..7] == "module ") {
import std.meta : AliasSeq;
alias getMethod = AliasSeq!();
} else {
alias getMethod = getMethod!(__traits(parent, x), name);
}
}

struct Dispatcher {
template opDispatch(string prefix) {
static auto opDispatch(alias context)() {
struct WithObject {
auto opDispatch(string name, A...)(A a) {
struct OverloadCaller {
auto opCall(Args...)(Args args) {
return getMethod!(context, 
prefix~"_"~name)(args);

}
}
OverloadCaller result;
return result;
}
}
return WithObject();
}
}
}

So, the ugly:

1) Instead of just Dispatcher.X, we need to give Dispatcher a 
context from where to look for X_. That's the curly 
brackets in Dispatcher.X!({}).


2) The bug I mentioned. The whole OverloadCaller deal is a 
silly workaround for WithObject's opDispatch not being called 
correctly by DMD. That's also why WithObject's opDispatch takes 
(A...)(A a). I'll be filing this, of course.


3) with doesn't correctly handle static opDispatch. I'll be 
filing a bug for that as well.


We could fix 1) by introducing a new magic identifier - 
something like __CONTEXT__, which would work somewhat like 
__FUNCTION__, but be useful for reflection with __traits. I've 
played a little with this idea, but I'm not ready to make a PR 
with it.


With 1), 2) and 3) fixed, the code would look like this (only 
changed code included):


unittest {
with (Dispatcher.X) {
A(1);
A("a");
B(2);
C_Q(3);
}
}

struct Dispatcher {
struct opDispatch(string prefix, alias context = 
__CONTEXT__) {
static auto opDispatch(string name, Args...)(Args args) 
{

 return getMethod!(context, prefix~"_"~name)(args);
}
}
}

I think that's kinda neat, TBH.

--
  Simen



Thanks, I haven't messed with it but it by your examples it 
should do what I want...


I actually probably need the use of .'s turned in to _'s... so I 
can write stuff like


A.B.C.D and it all goes to X.A_B_C_D.

I'm not sure if A.B.C.D would get dispatched as a whole or just 
in part though(e.g., is it treated as A.(B.(C.D)) or (A.B).C).D 
or A.B.C.D) which would require some type of chaining dispatcher 
I guess).


In any case it helps with my specific problem. I like the idea of 
_CONTEXT_ and it might be usable in other areas.


Thanks.


Re: emulate with

2019-05-31 Thread Simen Kjærås via Digitalmars-d-learn

On Friday, 31 May 2019 at 07:17:22 UTC, Amex wrote:
What I'm talking about is that if A would be dispatched to, 
say, W!X where W handles the special dispatching by returning 
X_A rather than X.A.



I don't know if D can do this kinda stuff even though it would 
be rather simple as it would depend on with.


Of course D can! However, it's not really pretty, and I think I 
found a bug in the process.


This is my code that compiles and runs:

void X_A(int i) {}
void X_A(string s) {}
void X_B(int i) {}
void X_C_Q(int i) {}

unittest {
with (Dispatcher.X!({})) {
A(1);
A("a");
B(2);
C_Q(3);
}
}

template getMethod(alias x, string name) {
static if (__traits(hasMember, x, name)) {
alias getMethod = __traits(getMember, x, name);
} else static if (x.stringof[0..7] == "module ") {
import std.meta : AliasSeq;
alias getMethod = AliasSeq!();
} else {
alias getMethod = getMethod!(__traits(parent, x), name);
}
}

struct Dispatcher {
template opDispatch(string prefix) {
static auto opDispatch(alias context)() {
struct WithObject {
auto opDispatch(string name, A...)(A a) {
struct OverloadCaller {
auto opCall(Args...)(Args args) {
return getMethod!(context, 
prefix~"_"~name)(args);

}
}
OverloadCaller result;
return result;
}
}
return WithObject();
}
}
}

So, the ugly:

1) Instead of just Dispatcher.X, we need to give Dispatcher a 
context from where to look for X_. That's the curly 
brackets in Dispatcher.X!({}).


2) The bug I mentioned. The whole OverloadCaller deal is a silly 
workaround for WithObject's opDispatch not being called correctly 
by DMD. That's also why WithObject's opDispatch takes (A...)(A 
a). I'll be filing this, of course.


3) with doesn't correctly handle static opDispatch. I'll be 
filing a bug for that as well.


We could fix 1) by introducing a new magic identifier - something 
like __CONTEXT__, which would work somewhat like __FUNCTION__, 
but be useful for reflection with __traits. I've played a little 
with this idea, but I'm not ready to make a PR with it.


With 1), 2) and 3) fixed, the code would look like this (only 
changed code included):


unittest {
with (Dispatcher.X) {
A(1);
A("a");
B(2);
C_Q(3);
}
}

struct Dispatcher {
struct opDispatch(string prefix, alias context = __CONTEXT__) 
{

static auto opDispatch(string name, Args...)(Args args) {
 return getMethod!(context, prefix~"_"~name)(args);
}
}
}

I think that's kinda neat, TBH.

--
  Simen


Re: emulate with

2019-05-31 Thread KnightMare via Digitalmars-d-learn
imo for parts of names such things will never appear.. names, 
subnames, overloading.. hell no


but I want Kotlin lambdas
https://kotlinlang.org/docs/reference/lambdas.html
I want more:
Function literals with receiver
it: implicit name of a single parameter
Passing a lambda to the last parameter
than will appear
https://ask.ericlin.info/post/2017/06/subtle-differences-between-kotlins-with-apply-let-also-and-run/
https://medium.com/tompee/idiomatic-kotlin-lambdas-with-receiver-and-dsl-3cd3348e1235



Re: Emulate C's (polymorphic) NULL type

2016-06-06 Thread Alex Parrill via Digitalmars-d-learn

On Monday, 6 June 2016 at 18:33:36 UTC, ParticlePeter wrote:

On Monday, 6 June 2016 at 16:19:02 UTC, Alex Parrill wrote:

On Monday, 6 June 2016 at 09:43:23 UTC, ParticlePeter wrote:

In C NULL can be used as integer as well as null pointer.
Is there a way to create such a type in D?

The type should have only one value which is obviously 
(0/null).
A extern( C ) function should be able to take it as either 
one.


Overloaded enum pops into my mind as example:
enum NULL = 0;
enum NULL = null;


Is this possible somehow?


I already asked about this: 
https://forum.dlang.org/post/bnkqevhyxwdjjxsct...@forum.dlang.org


Tldr; doesn't seem to be possible without multiple alias this 
or using ABI hacks.


O.k., my web search didn't find that topic. The last reply 
looks promising, wouldn't that work?


That's the ABI hack I mentioned. It abuses the fact that on most 
hardware and compiled, a pointer and a structure containing a 
single pointer have the same binary representation. It will 
likely work, but it isn't guarenteed.


Re: Emulate C's (polymorphic) NULL type

2016-06-06 Thread ParticlePeter via Digitalmars-d-learn

On Monday, 6 June 2016 at 18:33:36 UTC, ParticlePeter wrote:

On Monday, 6 June 2016 at 16:19:02 UTC, Alex Parrill wrote:

On Monday, 6 June 2016 at 09:43:23 UTC, ParticlePeter wrote:

In C NULL can be used as integer as well as null pointer.
Is there a way to create such a type in D?

The type should have only one value which is obviously 
(0/null).
A extern( C ) function should be able to take it as either 
one.


Overloaded enum pops into my mind as example:
enum NULL = 0;
enum NULL = null;


Is this possible somehow?


I already asked about this: 
https://forum.dlang.org/post/bnkqevhyxwdjjxsct...@forum.dlang.org


Tldr; doesn't seem to be possible without multiple alias this 
or using ABI hacks.


O.k., my web search didn't find that topic. The last reply 
looks promising, wouldn't that work?


Lets bump it and discuss there.


Re: Emulate C's (polymorphic) NULL type

2016-06-06 Thread ParticlePeter via Digitalmars-d-learn

On Monday, 6 June 2016 at 16:19:02 UTC, Alex Parrill wrote:

On Monday, 6 June 2016 at 09:43:23 UTC, ParticlePeter wrote:

In C NULL can be used as integer as well as null pointer.
Is there a way to create such a type in D?

The type should have only one value which is obviously 
(0/null).

A extern( C ) function should be able to take it as either one.

Overloaded enum pops into my mind as example:
enum NULL = 0;
enum NULL = null;


Is this possible somehow?


I already asked about this: 
https://forum.dlang.org/post/bnkqevhyxwdjjxsct...@forum.dlang.org


Tldr; doesn't seem to be possible without multiple alias this 
or using ABI hacks.


O.k., my web search didn't find that topic. The last reply looks 
promising, wouldn't that work?


Re: Emulate C's (polymorphic) NULL type

2016-06-06 Thread Alex Parrill via Digitalmars-d-learn

On Monday, 6 June 2016 at 09:43:23 UTC, ParticlePeter wrote:

In C NULL can be used as integer as well as null pointer.
Is there a way to create such a type in D?

The type should have only one value which is obviously (0/null).
A extern( C ) function should be able to take it as either one.

Overloaded enum pops into my mind as example:
enum NULL = 0;
enum NULL = null;


Is this possible somehow?


I already asked about this: 
https://forum.dlang.org/post/bnkqevhyxwdjjxsct...@forum.dlang.org


Tldr; doesn't seem to be possible without multiple alias this or 
using ABI hacks.


Re: Emulate C's (polymorphic) NULL type

2016-06-06 Thread Anonymouse via Digitalmars-d-learn

On Monday, 6 June 2016 at 12:09:33 UTC, ParticlePeter wrote:
I don't see the connection here, you introduced two symbols 
with two different types. I want one symbol which can pose as 
two different (constant) types.


Ah, my apologies, I misunderstood the question.


Re: Emulate C's (polymorphic) NULL type

2016-06-06 Thread ParticlePeter via Digitalmars-d-learn

On Monday, 6 June 2016 at 11:40:11 UTC, Anonymouse wrote:

On Monday, 6 June 2016 at 09:43:23 UTC, ParticlePeter wrote:

In C NULL can be used as integer as well as null pointer.
Is there a way to create such a type in D?

The type should have only one value which is obviously 
(0/null).

A extern( C ) function should be able to take it as either one.

Overloaded enum pops into my mind as example:
enum NULL = 0;
enum NULL = null;


Is this possible somehow?


If you want it for use in logical expressions then implicit 
boolean conversion will treat them as the same.


https://dpaste.dzfl.pl/d82f60657c37


I don't see the connection here, you introduced two symbols with 
two different types. I want one symbol which can pose as two 
different (constant) types.


Re: Emulate C's (polymorphic) NULL type

2016-06-06 Thread Anonymouse via Digitalmars-d-learn

On Monday, 6 June 2016 at 09:43:23 UTC, ParticlePeter wrote:

In C NULL can be used as integer as well as null pointer.
Is there a way to create such a type in D?

The type should have only one value which is obviously (0/null).
A extern( C ) function should be able to take it as either one.

Overloaded enum pops into my mind as example:
enum NULL = 0;
enum NULL = null;


Is this possible somehow?


If you want it for use in logical expressions then implicit 
boolean conversion will treat them as the same.


https://dpaste.dzfl.pl/d82f60657c37



Re: Emulate C's (polymorphic) NULL type

2016-06-06 Thread Anonymouse via Digitalmars-d-learn

On Monday, 6 June 2016 at 09:43:23 UTC, ParticlePeter wrote:

A extern( C ) function should be able to take it as either one.


Missed this bit. Not sure about that one.