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Partition a sequence into groups linearly by predicate

Partitions a sequence into groups linearly by predicate. I use this for breaking up my lazy record parsing with sequences into entity-sized chunks which are then easily digestible. Note: Edited back from the previous edit as these were heavily profiled and yield! tends to be slow. Edit #2: Now correctly using "use" instead of "let" for sequence.GetEnumerator () (Thanks Vladimir Matveev)

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let partition inclusive f (xs : #seq<_>) =
      let iter = xs.GetEnumerator()
      let rec loop () =
         seq {
            let rec innerLoop more =
               [
                  if more then
                     if not <| f iter.Current then
                        yield iter.Current
                        yield! innerLoop (iter.MoveNext())
                     elif inclusive then
                        yield iter.Current
               ]
            while iter.MoveNext() do
               yield innerLoop true
         }
      loop ()

module Seq =
    /// Partition into groups linearly by predicate (drops the partition element)
    /// ex. partitionLinear (fun x -> x = 1) [2; 3; 4; 5; 1; 2; 3; 4; 5]
    /// val it : seq<int list> = seq [[2; 3; 4; 5]; [2; 3; 4; 5]]
    let partitionLinear f xs = partition false f xs
    /// Partition into groups linearly by predicate (partition element inclusive)
    /// ex. partitionLinearInclusive (fun x -> x = 1) [2; 3; 4; 5; 1; 2; 3; 4; 5]
    /// val it : seq<int list> = seq [[2; 3; 4; 5; 1]; [2; 3; 4; 5]]
    let partitionLinearInclusive f xs = partition true f xs

val partition : inclusive:bool -> f:('a -> bool) -> xs:#seq<'a> -> seq<'a list>

Full name: Script.partition

val inclusive : bool

val f : ('a -> bool)

val xs : #seq<'a>

Multiple items
val seq : sequence:seq<'T> -> seq<'T>

Full name: Microsoft.FSharp.Core.Operators.seq

--------------------
type seq<'T> = System.Collections.Generic.IEnumerable<'T>

Full name: Microsoft.FSharp.Collections.seq<_>

val iter : System.Collections.Generic.IEnumerator<'a>

System.Collections.Generic.IEnumerable.GetEnumerator() : System.Collections.Generic.IEnumerator<'a>

val loop : (unit -> seq<'a list>)

val innerLoop : (bool -> 'a list)

val more : bool

val not : value:bool -> bool

Full name: Microsoft.FSharp.Core.Operators.not

property System.Collections.Generic.IEnumerator.Current: 'a

System.Collections.IEnumerator.MoveNext() : bool

Multiple items
module Seq

from Script

--------------------
module Seq

from Microsoft.FSharp.Collections

val partitionLinear : f:('a -> bool) -> xs:seq<'a> -> seq<'a list>

Full name: Script.Seq.partitionLinear

Partition into groups linearly by predicate (drops the partition element)
ex. partitionLinear (fun x -> x = 1) [2; 3; 4; 5; 1; 2; 3; 4; 5]
val it : seq<int list> = seq [[2; 3; 4; 5]; [2; 3; 4; 5]]

val xs : seq<'a>

val partitionLinearInclusive : f:('a -> bool) -> xs:seq<'a> -> seq<'a list>

Full name: Script.Seq.partitionLinearInclusive

Partition into groups linearly by predicate (partition element inclusive)
ex. partitionLinearInclusive (fun x -> x = 1) [2; 3; 4; 5; 1; 2; 3; 4; 5]
val it : seq<int list> = seq [[2; 3; 4; 5; 1]; [2; 3; 4; 5]]

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More information

Link:	http://fssnip.net/4q
Posted:	12 years ago
Author:	Rick Minerich
Tags:	seq , sequences , collections , grouping