Re: C++ std::string_view equivalent in D?
On Wednesday, 21 February 2018 at 10:43:14 UTC, 0x wrote: Gotta save this too. [BTW how do I post a thumbs up emoji]
Re: C++ std::string_view equivalent in D?
On 21/02/2018 10:43 AM, 0x wrote:
On Wednesday, 21 February 2018 at 10:24:39 UTC, ketmar wrote:
0x wrote:
[...]
and that is exactly what slices are for! ;-)
you are probably better to use `const(char)[]`, tho. like this:
// don't store `s`, as it's contents may change after exiting of
`myfunc`
// (this is what `const` implies here)
void myfunc (const(char)[] s) { ... }
...
string s = "test string";
myfunc(s); // yep, this works
s = s[2..4]; // this doesn't allocate
myfunc(s);
myfunc(s[3..6]); // or this, it doesn't allocate
myfunc("abc"); // or this, doesn't allocate
you got the idea.
Gotta save this too.
[BTW how do I post a thumbs up emoji]
+X (typically just 1) means that you agree.
But here we just say "thanks". This "forum" is backed by an NNTP server,
so lots of the more newer concepts don't exist here.
Re: C++ std::string_view equivalent in D?
On Wednesday, 21 February 2018 at 10:24:39 UTC, ketmar wrote:
0x wrote:
[...]
and that is exactly what slices are for! ;-)
you are probably better to use `const(char)[]`, tho. like this:
// don't store `s`, as it's contents may change after exiting
of `myfunc`
// (this is what `const` implies here)
void myfunc (const(char)[] s) { ... }
...
string s = "test string";
myfunc(s); // yep, this works
s = s[2..4]; // this doesn't allocate
myfunc(s);
myfunc(s[3..6]); // or this, it doesn't allocate
myfunc("abc"); // or this, doesn't allocate
you got the idea.
Gotta save this too.
[BTW how do I post a thumbs up emoji]
Re: C++ std::string_view equivalent in D?
On Wednesday, 21 February 2018 at 09:21:58 UTC, 0x wrote: What is the equivalent of C++17 std::string_view (an object that can refer to a constant contiguous sequence of char-like objects with the first element of the sequence at position zero) in D? PS: I'm getting back to D after years (since DMD 1 days). A lot changes since v1.0. Thanks guys @all. I completed the task. Glad to know there are lots people helping out here.
Re: C++ std::string_view equivalent in D?
On 21/02/2018 10:41 AM, 0x wrote: On Wednesday, 21 February 2018 at 09:21:58 UTC, 0x wrote: What is the equivalent of C++17 std::string_view (an object that can refer to a constant contiguous sequence of char-like objects with the first element of the sequence at position zero) in D? PS: I'm getting back to D after years (since DMD 1 days). A lot changes since v1.0. Thanks guys @all. I completed the task. Glad to know there are lots people helping out here. Hop on to IRC (FreeNode #d) or Discord https://discord.gg/sVMHUD (invite expires in a day) if you'd like a more interactive conversation :)
Re: C++ std::string_view equivalent in D?
On Wednesday, 21 February 2018 at 10:22:56 UTC, rikki cattermole wrote: On 21/02/2018 10:17 AM, 0x wrote: On Wednesday, 21 February 2018 at 09:21:58 UTC, 0x wrote: What is the equivalent of C++17 std::string_view (an object that can refer to a constant contiguous sequence of char-like objects with the first element of the sequence at position zero) in D? PS: I'm getting back to D after years (since DMD 1 days). A lot changes since v1.0. Wow! Thanks guys. Those are handy, but I specifically want to do something like: ``` string_view sv = "some string"; ``` string sv = "some string"; assert(sv.length == 11); Or just "some string".length ;) Thanks, it took time before I updated my reply to prevous answers. I didn't see these before I did. [I'm not that dumb] :winks:
Re: C++ std::string_view equivalent in D?
On Wednesday, 21 February 2018 at 10:23:23 UTC, Jonathan M Davis wrote: As I said in my previous response, read this article: https://dlang.org/articles/d-array-article.html Sorry, I didn't see this before I replied. Had I, I wouldn't have done that. string sv = "some string"; then _zero_ heap allocations take place. I think u've answered my question.
Re: C++ std::string_view equivalent in D?
0x wrote:
On Wednesday, 21 February 2018 at 09:21:58 UTC, 0x wrote:
What is the equivalent of C++17 std::string_view (an object that can
refer to a constant contiguous sequence of char-like objects with the
first element of the sequence at position zero) in D?
PS: I'm getting back to D after years (since DMD 1 days). A lot changes
since v1.0.
Wow! Thanks guys.
Those are handy, but I specifically want to do something like:
```
string_view sv = "some string";
```
So I can query it's size, make it point to sth else, use it in callbacks
etc. Of course I'm aware of scoping etc...
I'm NOT doing any dynamic allocations, I just want a situation where a
string allocation string would be a little bit expensive.
and that is exactly what slices are for! ;-)
you are probably better to use `const(char)[]`, tho. like this:
// don't store `s`, as it's contents may change after exiting of
`myfunc`
// (this is what `const` implies here)
void myfunc (const(char)[] s) { ... }
...
string s = "test string";
myfunc(s); // yep, this works
s = s[2..4]; // this doesn't allocate
myfunc(s);
myfunc(s[3..6]); // or this, it doesn't allocate
myfunc("abc"); // or this, doesn't allocate
you got the idea.
Re: C++ std::string_view equivalent in D?
On 21/02/2018 10:17 AM, 0x wrote: On Wednesday, 21 February 2018 at 09:21:58 UTC, 0x wrote: What is the equivalent of C++17 std::string_view (an object that can refer to a constant contiguous sequence of char-like objects with the first element of the sequence at position zero) in D? PS: I'm getting back to D after years (since DMD 1 days). A lot changes since v1.0. Wow! Thanks guys. Those are handy, but I specifically want to do something like: ``` string_view sv = "some string"; ``` string sv = "some string"; assert(sv.length == 11); Or just "some string".length ;)
Re: C++ std::string_view equivalent in D?
On Wednesday, February 21, 2018 10:17:55 0x via Digitalmars-d-learn wrote: > On Wednesday, 21 February 2018 at 09:21:58 UTC, 0x wrote: > > What is the equivalent of C++17 std::string_view (an object > > that can refer to a constant contiguous sequence of char-like > > objects with the first element of the sequence at position > > zero) in D? > > > > PS: I'm getting back to D after years (since DMD 1 days). A lot > > changes since v1.0. > > Wow! Thanks guys. > Those are handy, but I specifically want to do something like: > > ``` > string_view sv = "some string"; > ``` > So I can query it's size, make it point to sth else, use it in > callbacks etc. Of course I'm aware of scoping etc... > > I'm NOT doing any dynamic allocations, I just want a situation > where a string allocation string would be a little bit expensive. > > > [I believe I still have to study D more in that case to come up > with sth better, enjoying my ride so far] As I said in my previous response, read this article: https://dlang.org/articles/d-array-article.html You clearly do not understand at all how strings work in D. Strings in D basically _are_ string_views where most strings have the actual memory buffer managed by the GC. If you do string sv = "some string"; then _zero_ heap allocations take place. - Jonathan M Davis
C++ std::string_view equivalent in D?
On Wednesday, 21 February 2018 at 09:21:58 UTC, 0x wrote: What is the equivalent of C++17 std::string_view (an object that can refer to a constant contiguous sequence of char-like objects with the first element of the sequence at position zero) in D? PS: I'm getting back to D after years (since DMD 1 days). A lot changes since v1.0. Wow! Thanks guys. Those are handy, but I specifically want to do something like: ``` string_view sv = "some string"; ``` So I can query it's size, make it point to sth else, use it in callbacks etc. Of course I'm aware of scoping etc... I'm NOT doing any dynamic allocations, I just want a situation where a string allocation string would be a little bit expensive. [I believe I still have to study D more in that case to come up with sth better, enjoying my ride so far]
Re: C++ std::string_view equivalent in D?
On Wednesday, February 21, 2018 09:21:58 0x via Digitalmars-d-learn
wrote:
> What is the equivalent of C++17 std::string_view (an object that
> can refer to a constant contiguous sequence of char-like objects
> with the first element of the sequence at position zero) in D?
>
> PS: I'm getting back to D after years (since DMD 1 days). A lot
> changes since v1.0.
strings in D are that way by their very nature, because they're dynamic
arrays, and in D, dynamic arrays are just poiner and a length. Effectively,
a dynamic array is
struct DynamicArray(T)
{
size_t length;
T* ptr;
}
They're slices of some piece of memory - usually GC-allocated memory, though
you can slice any memory and get a dynamic array out of it. I'd suggest
reading this article:
https://dlang.org/articles/d-array-article.html
It does not use the official terminology, because it refers to the
GC-managed buffer as the dynamic array rather than the T[] as being the
dynamic array (whereas the official terminology is that T[] is a dynamic
array, regardless of what memory it's a slice of), but otherwise, what it
says is quite good and should give you a solid idea of how arrays work in D.
- Jonathan M Davis
Re: C++ std::string_view equivalent in D?
On Wednesday, 21 February 2018 at 09:21:58 UTC, 0x wrote: What is the equivalent of C++17 std::string_view (an object that can refer to a constant contiguous sequence of char-like objects with the first element of the sequence at position zero) in D? PS: I'm getting back to D after years (since DMD 1 days). A lot changes since v1.0. Strings were always slices in D even in version 1.0, what's changed is that string data is immutable now - guaranteed to not change.
Re: C++ std::string_view equivalent in D?
On Wednesday, 21 February 2018 at 09:21:58 UTC, 0x wrote: What is the equivalent of C++17 std::string_view (an object that can refer to a constant contiguous sequence of char-like objects with the first element of the sequence at position zero) in D? PS: I'm getting back to D after years (since DMD 1 days). A lot changes since v1.0. Perhaps you are looking for slices: https://dlang.org/spec/arrays.html#slicing?
Re: C++ std::string_view equivalent in D?
On 21/02/2018 9:21 AM, 0x wrote: What is the equivalent of C++17 std::string_view (an object that can refer to a constant contiguous sequence of char-like objects with the first element of the sequence at position zero) in D? PS: I'm getting back to D after years (since DMD 1 days). A lot changes since v1.0. Think of string_view as a poor man's slice support. Slices are essentially just dynamic arrays, a length and a pointer. char* ptr = cast(char*)malloc(32); char[] array = ptr[0 .. 32]; char[] anotherArray = array[16 .. $]; assert(anotherArray.length == 16); It isn't limited to just char's either :)
C++ std::string_view equivalent in D?
What is the equivalent of C++17 std::string_view (an object that can refer to a constant contiguous sequence of char-like objects with the first element of the sequence at position zero) in D? PS: I'm getting back to D after years (since DMD 1 days). A lot changes since v1.0.
