• Andrei Alexandrescu (2/2) Mar 01 2017 May be worth discussing in here:
• qznc (11/13) Mar 02 2017 I don't understand the use case. PR #5153 seems to be about
• Andrei Alexandrescu (5/17) Mar 02 2017 Yah, parsing would be an obvious application. Others such as
• Dukc (15/17) Mar 03 2017 //My understanding of the concept, is this correct?
• Dukc (2/10) Mar 03 2017
• Andrei Alexandrescu (2/3) Mar 03 2017 should be iota(5).lookaround!(1, 2)
• Dukc (4/6) Mar 03 2017 Almost similar to this: https://github.com/dlang/phobos/pull/4027
• Seb (5/12) Mar 03 2017 My PR even included such a circular buffer until Andrei suggested
• Andrei Alexandrescu (2/7) Mar 03 2017 Yes! cc @wilzbach

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

May be worth discussing in here: 
https://issues.dlang.org/show_bug.cgi?id=17238 -- Andrei

qznc <qznc web.de> writes:

On Thursday, 2 March 2017 at 01:44:19 UTC, Andrei Alexandrescu 
wrote:
 May be worth discussing in here: 
 https://issues.dlang.org/show_bug.cgi?id=17238 -- Andrei


getting the last element, not about some lookahead. When I think 
about lookahead, I always think of parsers. If the lexer provides 
an input range of tokens, my recursive descent parser might need 
3 tokens lookahead, for example. For the lexer input a "push back 
a character into my input" is more convenient.

Should it give some performance guarantees? I guess, we don't 
want to refresh the buffers at every popFront, so it would 
probably be as lazy as possible.

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 3/2/17 7:51 AM, qznc wrote:
 On Thursday, 2 March 2017 at 01:44:19 UTC, Andrei Alexandrescu wrote:
 May be worth discussing in here:
 https://issues.dlang.org/show_bug.cgi?id=17238 -- Andrei


 last element, not about some lookahead. When I think about lookahead, I
 always think of parsers. If the lexer provides an input range of tokens,
 my recursive descent parser might need 3 tokens lookahead, for example.
 For the lexer input a "push back a character into my input" is more
 convenient.

Yah, parsing would be an obvious application. Others such as 
adjacentFind might also benefit.

 Should it give some performance guarantees? I guess, we don't want to
 refresh the buffers at every popFront, so it would probably be as lazy
 as possible.

Yah, a circular buffer should help here.


Andrei

Dukc <ajieskola gmail.com> writes:

On Thursday, 2 March 2017 at 01:44:19 UTC, Andrei Alexandrescu 
wrote:
 May be worth discussing in here: 
 https://issues.dlang.org/show_bug.cgi?id=17238 -- Andrei

//My understanding of the concept, is this correct?
assert(iota(5).lookAhead(1, 2).array ==
[   [0, 1],
     [0, 1, 2],
     [0, 1, 2, 3],
     [1, 2, 3, 4],
     [2, 3, 4],
     [3, 4],
     [4]
]);

I would prefer if the second argument meant length, not distance 
to look back. So the call equivalent to the one above would be 
lookAhead(-2, 4).

Dukc <ajieskola gmail.com> writes:

On Friday, 3 March 2017 at 11:22:37 UTC, Dukc wrote:
 [snip]

correction:
 assert(iota(5).lookAhead(1, 2).array ==
 [   [0, 1],
     [0, 1, 2],
     [0, 1, 2, 3],
     [1, 2, 3, 4],
     [2, 3, 4]
 ]);

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 3/3/17 6:22 AM, Dukc wrote:
 iota(5).lookAhead(1, 2)

should be iota(5).lookaround!(1, 2)

Dukc <ajieskola gmail.com> writes:

On Thursday, 2 March 2017 at 01:44:19 UTC, Andrei Alexandrescu 
wrote:
 May be worth discussing in here: 
 https://issues.dlang.org/show_bug.cgi?id=17238 -- Andrei

Almost similar to this: https://github.com/dlang/phobos/pull/4027

Perhaps we should use that as base?

Seb <seb wilzba.ch> writes:

On Friday, 3 March 2017 at 11:56:26 UTC, Dukc wrote:
 On Thursday, 2 March 2017 at 01:44:19 UTC, Andrei Alexandrescu 
 wrote:
 May be worth discussing in here: 
 https://issues.dlang.org/show_bug.cgi?id=17238 -- Andrei

 Almost similar to this: 
 https://github.com/dlang/phobos/pull/4027

 Perhaps we should use that as base?

My PR even included such a circular buffer until Andrei suggested 
to move it to a separate PR.
However, I think we are all misunderstanding  Andrei. He isn't 
referring to a buffer here - have a look at the issue.

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 3/3/17 6:56 AM, Dukc wrote:
 On Thursday, 2 March 2017 at 01:44:19 UTC, Andrei Alexandrescu wrote:
 May be worth discussing in here:
 https://issues.dlang.org/show_bug.cgi?id=17238 -- Andrei

 Almost similar to this: https://github.com/dlang/phobos/pull/4027

 Perhaps we should use that as base?

Yes! cc  wilzbach