more code

Pentole/pervasives.fs

@@ -1,5 +1,6 @@
 namespace Pentole
 
+/// The initially opened module. 
 [<AutoOpen>]
 module Pervasives =
 
@@ -7,3 +8,10 @@ module Pervasives =
     /// The identity function.
     /// </summary>
     let identity = id
+
+    /// An active pattern that matches strings starting with a specified prefix.
+    let (|Prefix|_|) (p: string) (s: string) =
+        if s.StartsWith p then
+            s.Substring p.Length |> Some
+        else
+            None

Pentole/string.fs

@@ -1,18 +1,20 @@
-module Pentole.String
+namespace Pentole
 
-let split (separator: string) (target: string) : string list =
-    if System.String.IsNullOrEmpty separator  then
-        [target]
-    else
-        let slen = separator.Length
-        let rec split (acc: string list) (start_idx: int) =
-            match target.IndexOf(separator, start_idx) with
-            | -1 -> 
-                if start_idx < target.Length then
-                    target.Substring(start_idx) :: acc 
-                else  acc
-            | index ->
-                let part = target.Substring (start_idx, index - start_idx)
-                split (part :: acc) (index + slen) 
+module String =
 
-        split [] 0 |> List.rev
+    let split (separator: string) (target: string) : string list =
+        if System.String.IsNullOrEmpty separator  then
+            [target]
+        else
+            let slen = separator.Length
+            let rec split (acc: string list) (start_idx: int) =
+                match target.IndexOf(separator, start_idx) with
+                | -1 -> 
+                    if start_idx < target.Length then
+                        target.Substring(start_idx) :: acc 
+                    else  acc
+                | index ->
+                    let part = target.Substring (start_idx, index - start_idx)
+                    split (part :: acc) (index + slen) 
+
+            split [] 0 |> List.rev

Pentole/test_extensions.fs

@@ -2,6 +2,8 @@ namespace Pentole
 
 open NUnit.Framework
 
+type TestAttribute = NUnit.Framework.TestAttribute
+
 module Assert =
     let inline okEquals<'ok, 'err> (expected: 'ok) (got: Result<'ok, 'err>) =
         match got with