From b953a0e0c5b6990b0e81f2135794a4e6ac81a2b6 Mon Sep 17 00:00:00 2001
From: gusty <1261319+gusty@users.noreply.github.com>
Date: Tue, 8 Oct 2024 06:46:16 +0200
Subject: [PATCH] + SeqT.head and SeqT.tryHead

---
 src/FSharpPlus/Data/Seq.fs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/FSharpPlus/Data/Seq.fs b/src/FSharpPlus/Data/Seq.fs
index 3c950a5df..5a7ea5817 100644
--- a/src/FSharpPlus/Data/Seq.fs
+++ b/src/FSharpPlus/Data/Seq.fs
@@ -764,6 +764,14 @@ module SeqT_V2 =
     let inline iteri<'T, .. > (f: int -> 'T -> unit)      (source: SeqT<'``Monad<bool>``, 'T>) : '``Monad<unit>`` = iteriM (fun i x -> result (f i x)) source
     let inline iter<'T, .. > f (source: SeqT<'``Monad<bool>``, 'T>) : '``Monad<unit>`` = iterM (f >> result) source
 
+    let inline tryHead (source: SeqT<'``Monad<bool>``, 'T>) : '``Monad<'T option>`` =
+        use ie = (source :> IEnumerableM<'``Monad<bool>``, 'T>).GetEnumerator ()
+        Bind.Invoke (ie.MoveNext ()) (fun b -> Return.Invoke (if b then Some ie.Current else None))
+
+    let inline head (source: SeqT<'``Monad<bool>``, 'T>) : '``Monad<'T>`` =
+        use ie = (source :> IEnumerableM<'``Monad<bool>``, 'T>).GetEnumerator ()
+        Bind.Invoke (ie.MoveNext ()) (fun b -> Return.Invoke (if b then ie.Current else invalidArg (nameof source) "The input sequence was empty."))
+    
     let inline internal tryPickMAndMap<'T, 'U, .. > (f: 'T -> '``Monad<'U option>``) (source: SeqT<'``Monad<bool>``, 'T>) (postMap: 'U option -> 'V) : '``Monad<'V>`` = innerMonad2<_, '``Monad<unit>``> () {
         use ie = (source :> IEnumerableM<'``Monad<bool>``, 'T>).GetEnumerator ()
         let! move = ie.MoveNext ()