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March 04, 2019 InsertBefore in DList of structs | ||||
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I have a DList of structs, DataPoint, ordered by a struct field, time. I'm trying to insert a new entry preserving order, so I'm trying to use `until` to find the insertion point and `insertBefore` with the result. struct DataPoint { immutable ulong time; ulong value; } void main() { DList!DataPoint dataPoints; void incrementAt(ulong time) { auto dataPoint = until!(dp => dp.time >= time)(dataPoints); if (dataPoint.time == time) { ++dataPoint.value; } else { dataPoints.insertBefore(dataPoint, DataPoint(time, 1)); } } } But I'm getting: /dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/searching.d(4898): Error: template instance `onlineapp.main.incrementAt.Until!(__lambda2, DList!(DataPoint), void)` does not match template declaration Until(alias pred, Range, Sentinel) if (isInputRange!Range) onlineapp.d(14): Error: template instance `onlineapp.main.incrementAt.until!((dp) => dp.time >= time, DList!(DataPoint))` error instantiating |
March 04, 2019 Re: InsertBefore in DList of structs | ||||
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Posted in reply to r-const-dev | On 04.03.2019 11:14, r-const-dev wrote: > I have a DList of structs, DataPoint, ordered by a struct field, time. I'm trying to insert a new entry preserving order, so I'm trying to use `until` to find the insertion point and `insertBefore` with the result. > > struct DataPoint { > immutable ulong time; > ulong value; > } > > void main() { > DList!DataPoint dataPoints; > void incrementAt(ulong time) { > auto dataPoint = until!(dp => dp.time >= time)(dataPoints); > if (dataPoint.time == time) { > ++dataPoint.value; > } else { > dataPoints.insertBefore(dataPoint, DataPoint(time, 1)); > } > } > } > > But I'm getting: > > /dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/searching.d(4898): Error: template instance `onlineapp.main.incrementAt.Until!(__lambda2, DList!(DataPoint), void)` does not match template declaration Until(alias pred, Range, Sentinel) if (isInputRange!Range) > onlineapp.d(14): Error: template instance `onlineapp.main.incrementAt.until!((dp) => dp.time >= time, DList!(DataPoint))` error instantiating dataPoints itself isn't a range, you need to use dataPoints[]. Also insertStable needs DList.Range, not Until!... one. You can do something like this https://run.dlang.io/is/A2vZjW |
March 04, 2019 Re: InsertBefore in DList of structs | ||||
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Posted in reply to drug | On 04.03.2019 13:03, drug wrote: > insertStable needs DList.Range, not Until!... one. You can do something like this https://run.dlang.io/is/A2vZjW Oops, it was wrong example, I'd recommend this way - https://run.dlang.io/is/ugPL8j ``` import std.algorithm, std.container, std.stdio; struct DataPoint { immutable ulong time; ulong value; } void main() { auto dataPoints = DList!DataPoint([ DataPoint(10_000_000, 1), DataPoint(30_000_000, 3), DataPoint(40_000_000, 4), ]); auto time = 30_000_000; auto r = findSplit!((a, b) => a.time == b)(dataPoints[], [time]); auto dp = dataPoints[].find(r[1].front); writeln("before: ", dataPoints[]); dataPoints.insertBefore(dp, DataPoint(20_000_000, 2)); writeln("after: ", dataPoints[]); } ``` |
March 04, 2019 Re: InsertBefore in DList of structs | ||||
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Posted in reply to drug | On Monday, 4 March 2019 at 10:09:19 UTC, drug wrote:
> On 04.03.2019 13:03, drug wrote:
>> insertStable needs DList.Range, not Until!... one. You can do something like this https://run.dlang.io/is/A2vZjW
> Oops, it was wrong example, I'd recommend this way - https://run.dlang.io/is/ugPL8j
> ```
> import std.algorithm, std.container, std.stdio;
>
> struct DataPoint {
> immutable ulong time;
> ulong value;
> }
>
> void main() {
> auto dataPoints = DList!DataPoint([
> DataPoint(10_000_000, 1),
> DataPoint(30_000_000, 3),
> DataPoint(40_000_000, 4),
> ]);
>
> auto time = 30_000_000;
> auto r = findSplit!((a, b) => a.time == b)(dataPoints[], [time]);
>
> auto dp = dataPoints[].find(r[1].front);
> writeln("before: ", dataPoints[]);
> dataPoints.insertBefore(dp, DataPoint(20_000_000, 2));
> writeln("after: ", dataPoints[]);
> }
>
> ```
Thanks, seems that using dataPoints[] makes dataPoints usable as an range. How can I learn more about [] operator? I'm not sure I understand how is this documented in DList.
Find does the job! What's the difference between find and until?
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March 05, 2019 Re: InsertBefore in DList of structs | ||||
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Posted in reply to r-const-dev | On 05.03.2019 2:01, r-const-dev wrote: > > Thanks, seems that using dataPoints[] makes dataPoints usable as an range. How can I learn more about [] operator? I'm not sure I understand how is this documented in DList. dataPoints is an aggregate type variable, not a range and slice operator opSlice/[] returns a range of this aggregate type. I have no appropriate links unfortunately but these can be useful https://dlang.org/phobos/std_container_dlist.html#.DList.opSlice - this operator returns a range https://dlang.org/phobos/std_container_dlist.html#.DList.Range - this is range that allows to iterate over DList elements http://ddili.org/ders/d.en/ranges.html - intro to ranges > > Find does the job! What's the difference between find and until? `find` returns a range that starts from the key `until` returns a range of all elements before the key https://run.dlang.io/is/1kpOUx P.S. `findSplit` returns three ranges, first one contains all elements before the key like `until`, second range contains all elements that are equal to the key and third range contains the rest |
March 05, 2019 Re: InsertBefore in DList of structs | ||||
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Posted in reply to drug | On Tuesday, 5 March 2019 at 08:39:56 UTC, drug wrote:
> On 05.03.2019 2:01, r-const-dev wrote:
>> [...]
> dataPoints is an aggregate type variable, not a range and slice operator opSlice/[] returns a range of this aggregate type. I have no appropriate links unfortunately but these can be useful
> https://dlang.org/phobos/std_container_dlist.html#.DList.opSlice - this operator returns a range
> https://dlang.org/phobos/std_container_dlist.html#.DList.Range - this is
> range that allows to iterate over DList elements
> http://ddili.org/ders/d.en/ranges.html - intro to ranges
>> [...]
> `find` returns a range that starts from the key
> `until` returns a range of all elements before the key
> https://run.dlang.io/is/1kpOUx
>
> [...]
Thank you for clarifications, it makes sense to me now.
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