www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - InsertBefore in DList of structs

reply r-const-dev <r.const.dev gmail.com> writes:
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
Mar 04
parent reply drug <drug2004 bk.ru> writes:
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
Mar 04
parent reply drug <drug2004 bk.ru> writes:
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[]); } ```
Mar 04
parent reply r-const-dev <r.const.dev gmail.com> writes:
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?
Mar 04
parent reply drug <drug2004 bk.ru> writes:
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
Mar 05
parent r-const-dev <r.const.dev gmail.com> writes:
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.
Mar 05