I'd like to copy an array string into a appender!string() but I can't see how to do this without loop myself over the string array. Is there a native function or should I write it myself?

On Sunday, 21 September 2014 at 23:41:58 UTC, AsmMan wrote:
> I'd like to copy an array string into a appender!string() but I can't see how to do this without loop myself over the string array. Is there a native function or should I write it myself?

call:

auto app = appender!string();
	string[] s = ["foo", "baa"];
	app.put(s);

give a:

\src\phobos\std\conv.d(9,9): Error: static assert  "immutable(char) cannot be emplaced from a string." (b)

How do I fix it?

On Sun, Sep 21, 2014 at 11:41:56PM +0000, AsmMan via Digitalmars-d-learn wrote:
> I'd like to copy an array string into a appender!string() but I can't see how to do this without loop myself over the string array. Is there a native function or should I write it myself?

Try this:

	import std.array : appender;
	import std.algorithm : joiner, copy;

	string[] arr = ["ab", "cd", "efg"];
	auto app = appender!string();
	arr.joiner.copy(app);
	assert(app.data == "abcdefg");


T

-- 
One reason that few people are aware there are programs running the internet is that they never crash in any significant way: the free software underlying the internet is reliable to the point of invisibility. -- Glyn Moody, from the article "Giving it all away"

On Sun, 21 Sep 2014 23:41:56 +0000
AsmMan via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
wrote:

> I'd like to copy an array string into a appender!string() but I can't see how to do this without loop myself over the string array. Is there a native function or should I write it myself?

hm... '.put' should work. i.e.

  string s = `something`;
  auto ap = appender!string();
  ap.put(s);
  // now ap.data returns `something`

On Mon, 22 Sep 2014 02:51:41 +0300
ketmar via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
wrote:

sorry, forgot that. i misunderstood your question.

On Sunday, 21 September 2014 at 23:48:59 UTC, AsmMan wrote:
> On Sunday, 21 September 2014 at 23:41:58 UTC, AsmMan wrote:
>> I'd like to copy an array string into a appender!string() but I can't see how to do this without loop myself over the string array. Is there a native function or should I write it myself?
>
> call:
>
> auto app = appender!string();
> 	string[] s = ["foo", "baa"];
> 	app.put(s);
>
> give a:
>
> \src\phobos\std\conv.d(9,9): Error: static assert  "immutable(char) cannot be emplaced from a string." (b)
>
> How do I fix it?

put(app, s);

This is not an ideal solution, since Appender may reallocate several times when appending the array items. Ideally, appender itself should take a range of strings, so that it can preallocate memory for them only once.

On Monday, 22 September 2014 at 00:09:22 UTC, Vladimir Panteleev wrote:
> On Sunday, 21 September 2014 at 23:48:59 UTC, AsmMan wrote:
>> On Sunday, 21 September 2014 at 23:41:58 UTC, AsmMan wrote:
>>> I'd like to copy an array string into a appender!string() but I can't see how to do this without loop myself over the string array. Is there a native function or should I write it myself?
>>
>> call:
>>
>> auto app = appender!string();
>> 	string[] s = ["foo", "baa"];
>> 	app.put(s);
>>
>> give a:
>>
>> \src\phobos\std\conv.d(9,9): Error: static assert  "immutable(char) cannot be emplaced from a string." (b)
>>
>> How do I fix it?
>
> put(app, s);
>
> This is not an ideal solution, since Appender may reallocate several times when appending the array items. Ideally, appender itself should take a range of strings, so that it can preallocate memory for them only once.

this give undefined identifier: 'put' error. (std.array is already included, buffer.put(string) doesn't give same error)

The copy of an array doesn't happen often as string but do suggest to I want something else instead of appender?

On Monday, 22 September 2014 at 00:18:03 UTC, AsmMan wrote:
> this give undefined identifier: 'put' error. (std.array is already included, buffer.put(string) doesn't give same error)

You need to import std.range.

> The copy of an array doesn't happen often as string but do suggest to I want something else instead of appender?

No, I was just thinking aloud about how Appender could be improved in the future.

To minimize allocations right now, you could write your own put-like function which calls Appender.reserve.

On Monday, 22 September 2014 at 00:30:44 UTC, Vladimir Panteleev wrote:
> On Monday, 22 September 2014 at 00:18:03 UTC, AsmMan wrote:
>> this give undefined identifier: 'put' error. (std.array is already included, buffer.put(string) doesn't give same error)
>
> You need to import std.range.

Thanks, I was thinking std.array is enough

>> The copy of an array doesn't happen often as string but do suggest to I want something else instead of appender?
>
> No, I was just thinking aloud about how Appender could be improved in the future.
>
> To minimize allocations right now, you could write your own put-like function which calls Appender.reserve.

this is not critical (for now, I'm not doing any optmization) but I'll save the idea.

On Sunday, 21 September 2014 at 23:50:50 UTC, H. S. Teoh via Digitalmars-d-learn wrote:
> On Sun, Sep 21, 2014 at 11:41:56PM +0000, AsmMan via Digitalmars-d-learn wrote:
>> I'd like to copy an array string into a appender!string() but I can't
>> see how to do this without loop myself over the string array. Is there
>> a native function or should I write it myself?
>
> Try this:
>
> 	import std.array : appender;
> 	import std.algorithm : joiner, copy;
>
> 	string[] arr = ["ab", "cd", "efg"];
> 	auto app = appender!string();
> 	arr.joiner.copy(app);
> 	assert(app.data == "abcdefg");
>
>
> T

FYI, that's probably scary expensive in terms of encoding/decoding.

Using the "free" std.range.put should take care of everything, natively.