Hi,

I am from Ruby world where I can have `!` (or `?`) in method names: `!` indicates that a method would modify its object (`foo.upcase!` means `foo = foo.upcase`). ( I don't know if there is any official Ruby documentation on this convention though. )

In D I see `!` quite a lot. I have read the first 50 chapters in Ali's book but nowhere I see a note on `!`. It's about the compile thing, isn't it? E.g,

```
foo = formattedRead!"%s"(value);
```

But I also see `!` for some map/filter invocations. It's quite confusing me.

Can you please explain and give any link where I can learn more about these things?

Thanks a lot.

There are two types of arguments in D. The runtime one (which you are well aware of) and the compile time one. A compile time argument is a constant passed in during construction of a symbol.

But here is the thing, it isn't just limited to functions, you can have it on classes as well.

---
class Foo(bool b) {
	bool get() { return b; }
}

void main() {
	Foo!true v = new Foo!true;
	assert(v.get);
}
---

Same logic going on.

---
bool get(bool b)() {
	return b;
}

void main() {
	assert(get!true == true);
}
---

It can do more than a simple boolean being passed in, but that is the gist. Templates are wonderful (also read the spec!).

On Wednesday, 27 September 2017 at 14:23:01 UTC, Ky-Anh Huynh wrote:
> Hi,
>
> I am from Ruby world where I can have `!` (or `?`) in method names: `!` indicates that a method would modify its object (`foo.upcase!` means `foo = foo.upcase`). ( I don't know if there is any official Ruby documentation on this convention though. )
>
> In D I see `!` quite a lot. I have read the first 50 chapters in Ali's book but nowhere I see a note on `!`. It's about the compile thing, isn't it? E.g,
>
> ```
> foo = formattedRead!"%s"(value);
> ```
>
> But I also see `!` for some map/filter invocations. It's quite confusing me.
>
> Can you please explain and give any link where I can learn more about these things?
>
> Thanks a lot.

See also the following chapter in Ali's book:
http://ddili.org/ders/d.en/templates.html

On Wednesday, 27 September 2017 at 14:34:06 UTC, Eugene Wissner wrote:
>
> See also the following chapter in Ali's book:
> http://ddili.org/ders/d.en/templates.html

Thanks a lot. I will keep reading :)

On Wednesday, 27 September 2017 at 14:23:01 UTC, Ky-Anh Huynh wrote:
> Can you please explain and give any link where I can learn more about these things?
>
> Thanks a lot.

http://nomad.so/2013/07/templates-in-d-explained/

On 09/27/2017 08:33 AM, Ky-Anh Huynh wrote:
> On Wednesday, 27 September 2017 at 14:34:06 UTC, Eugene Wissner wrote:
>>
>> See also the following chapter in Ali's book:
>> http://ddili.org/ders/d.en/templates.html
>
> Thanks a lot. I will keep reading :)

The fact that such an important operator is explained so late in the book is due to the book's strong desire to have a linear flow.

Although binary ! appears before the templates chapter as to!int, format!"%s", etc., I decided to get to templates only after going through everything that could be templatized. (For example, even interfaces can be templates.) I don't claim this is the best choice but I'm happy that some people said that they found the linear flow useful. (I know that others would find it boring. :) )

If I were to write the book again, one other thing that I would explain earlier would be UFCS, and I would use much more of it in the examples. (UFCS was added to the language after I wrote most of the book.)

Ali

On Wednesday, 27 September 2017 at 17:58:27 UTC, Ali Çehreli wrote:
> On 09/27/2017 08:33 AM, Ky-Anh Huynh wrote:
> > [...]
> Wissner wrote:
> > [...]
>
> The fact that such an important operator is explained so late in the book is due to the book's strong desire to have a linear flow.
>
> [...]

ustad, guess you can still write the new ed. :-)

On 09/27/2017 03:06 PM, Mengu wrote:

> ustad, guess you can still write the new ed. :-)

Since you're still around, one of these days... :)

Ali

On Wednesday, 27 September 2017 at 14:34:06 UTC, Eugene Wissner wrote:
> On Wednesday, 27 September 2017 at 14:23:01 UTC, Ky-Anh Huynh wrote:
>>
>
> See also the following chapter in Ali's book:
> http://ddili.org/ders/d.en/templates.html

This chapter is what hooked me with D. Naming that chapter as "Templates for Human Beings" won't be an exaggeration.