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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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open System
open System.Linq

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 (func : _ -> bool) (sequence : _ seq) : _ list seq =
        seq {
            use en = sequence.GetEnumerator ()
            let more = ref true
            while !more do
                let wasGood = ref true
                let sublist = 
                    [
                        while !wasGood && en.MoveNext() do
                            if not (func en.Current) then yield en.Current
                            else wasGood := false
                    ]
                if List.isEmpty sublist then more := false
                else yield sublist
        }

    /// 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 (func : _ -> bool) (sequence : _ seq) : _ list seq =
        seq {
            use en = sequence.GetEnumerator ()
            let more = ref true
            while !more do
                let wasGood = ref true
                let sublist = 
                    [
                        while !wasGood && en.MoveNext() do
                            if func en.Current then wasGood := false
                            yield en.Current
                    ]
                if List.isEmpty sublist then more := false
                else yield sublist
        }

namespace System

namespace System.Linq

Multiple items
module Seq

from Script

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

from Microsoft.FSharp.Collections

val partitionLinear : func:('a -> bool) -> sequence: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 func : ('a -> bool)

type bool = Boolean

Full name: Microsoft.FSharp.Core.bool

val sequence : seq<'a>

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

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

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

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

type 'T list = List<'T>

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

val en : Collections.Generic.IEnumerator<'a>

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

val more : bool ref

Multiple items
val ref : value:'T -> 'T ref

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

--------------------
type 'T ref = Ref<'T>

Full name: Microsoft.FSharp.Core.ref<_>

val wasGood : bool ref

val sublist : 'a list

Collections.IEnumerator.MoveNext() : bool

val not : value:bool -> bool

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

property Collections.Generic.IEnumerator.Current: 'a

Multiple items
module List

from Microsoft.FSharp.Collections

--------------------
type List<'T> =
  | ( [] )
  | ( :: ) of Head: 'T * Tail: 'T list
  interface IEnumerable
  interface IEnumerable<'T>
  member Head : 'T
  member IsEmpty : bool
  member Item : index:int -> 'T with get
  member Length : int
  member Tail : 'T list
  static member Cons : head:'T * tail:'T list -> 'T list
  static member Empty : 'T list

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

val isEmpty : list:'T list -> bool

Full name: Microsoft.FSharp.Collections.List.isEmpty

val partitionLinearInclusive : func:('a -> bool) -> sequence: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:	13 years ago
Author:	Rick Minerich
Tags:	seq , sequences , collections , grouping