From 41bb755e157bbe244a85627bf74752259e25cd3f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kevin=20Hovs=C3=A4ter?= <kevin@hovsater.com>
Date: Tue, 10 Dec 2024 08:29:47 +0100
Subject: [PATCH 1/3] String.find/String.rfind USize proposal

---
 text/0000-usize-indexing | 50 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 text/0000-usize-indexing

diff --git a/text/0000-usize-indexing b/text/0000-usize-indexing
new file mode 100644
index 00000000..a4445397
--- /dev/null
+++ b/text/0000-usize-indexing
@@ -0,0 +1,50 @@
+- Feature Name: string_find_usize
+- Start Date: 2024-12-09
+- RFC PR: (leave this empty)
+- Pony Issue: (leave this empty)
+
+# Summary
+
+Change the return type of `String.find`  and `String.rfind` from `ISize` to `USize`, aligning its return type with `Array.find`.
+
+# Motivation
+
+The current return type of `String.find` and `String.rfind` is `ISize`, which stems from its historical behavior of returning `-1` when no match was found. However, these methods now return `error` for such cases. Returning `USize` makes more sense because indices are always non-negative, and it aligns with `Array.find`'s method signature.
+
+# Detailed design
+
+The method signature of [String.find](https://github.com/ponylang/ponyc/blob/736220a34364a864fe0fd1f091a85852ded84d23/packages/builtin/string.pony#L640) and [String.rfind](https://github.com/ponylang/ponyc/blob/736220a34364a864fe0fd1f091a85852ded84d23/packages/builtin/string.pony#L669) would change to return `USize` instead of `ISize`.
+
+Specifically, the method signatures would be changed from this:
+
+```pony
+fun find(s: String box, offset: ISize = 0, nth: USize = 0): ISize ?
+fun rfind(s: String box, offset: ISize = -1, nth: USize = 0): ISize ?
+```
+
+to this:
+
+```pony
+fun find(s: String box, offset: ISize = 0, nth: USize = 0): USize ?
+fun rfind(s: String box, offset: ISize = -1, nth: USize = 0): USize ?
+```
+
+# How We Teach This
+
+N/A
+
+# How We Test This
+
+Standard CI and the compiler should identify most areas that need to be addressed. Additionally, any documentation, code examples, and guides should be reviewed and updated to reflect the new behavior.
+
+# Drawbacks
+
+It's a breaking change as the method signature has to change. Existing code relying on `String.find` and `String.rfind` will need to be migrated.
+
+# Alternatives
+
+Keep the existing method signature to avoid breaking changes introduced by this proposal.
+
+# Unresolved questions
+
+N/A

From 674631057dcd605563dbbc1156460b02064dc97d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kevin=20Hovs=C3=A4ter?= <kevin@hovsater.com>
Date: Sun, 5 Jan 2025 09:30:49 +0100
Subject: [PATCH 2/3] fixup! String.find/String.rfind USize proposal

---
 text/0000-usize-indexing | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/text/0000-usize-indexing b/text/0000-usize-indexing
index a4445397..ee574689 100644
--- a/text/0000-usize-indexing
+++ b/text/0000-usize-indexing
@@ -31,7 +31,7 @@ fun rfind(s: String box, offset: ISize = -1, nth: USize = 0): USize ?
 
 # How We Teach This
 
-N/A
+Through the standard library documentation and the associated release notes.
 
 # How We Test This
 
@@ -47,4 +47,4 @@ Keep the existing method signature to avoid breaking changes introduced by this
 
 # Unresolved questions
 
-N/A
+None at this time.

From e85c0a9526771c5a8db55e0d4c21d5f3dd28f58d Mon Sep 17 00:00:00 2001
From: Sean T Allen <sean@seantallen.com>
Date: Thu, 16 Jan 2025 10:55:40 -0500
Subject: [PATCH 3/3] Update text/0000-usize-indexing

---
 text/0000-usize-indexing | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/text/0000-usize-indexing b/text/0000-usize-indexing
index ee574689..2a8c1984 100644
--- a/text/0000-usize-indexing
+++ b/text/0000-usize-indexing
@@ -35,7 +35,7 @@ Through the standard library documentation and the associated release notes.
 
 # How We Test This
 
-Standard CI and the compiler should identify most areas that need to be addressed. Additionally, any documentation, code examples, and guides should be reviewed and updated to reflect the new behavior.
+Standard CI and the compiler should identify any additional code areas that are needed. Sean T. Allen did a review of the tutorial, pony patterns, and the website and found no changes that would be needed to reflect the new behavior.
 
 # Drawbacks