From 00e03d8fb65119e736dae4db8335e1ac67aac23e Mon Sep 17 00:00:00 2001
From: tslil <tslil@posteo.de>
Date: Fri, 31 Oct 2025 12:19:33 +0000
Subject: Rework character and end implementations

---
 .../src/selection_functions/function_character.rs  | 64 ++++++++++++++++++----
 .../src/selection_functions/function_end.rs        | 50 +++++++++++++----
 rprt-engine/src/selection_functions/types.rs       |  4 +-
 3 files changed, 95 insertions(+), 23 deletions(-)

diff --git a/rprt-engine/src/selection_functions/function_character.rs b/rprt-engine/src/selection_functions/function_character.rs
index 3d9695f..0d0699f 100644
--- a/rprt-engine/src/selection_functions/function_character.rs
+++ b/rprt-engine/src/selection_functions/function_character.rs
@@ -4,7 +4,7 @@ use crate::selection_functions::types::{get_buffer, SFArguments, SFError, SFResu
 use crate::state::EditorState;
 
 selection_function_param! {
-    name: character_structural,
+    name: character,
     param_type: usize,
     niladic: |(param, es): (usize, &EditorState)| {
         let buf = get_buffer(es, es.current_buffer_id)?;
@@ -14,19 +14,15 @@ selection_function_param! {
 
         }) },
     monadic_rank0: |_, buffer_id, pos| Ok(Selection::Position {buffer_id, pos}),
-    monadic_rank1: |(param, _), buffer_id, int| Ok(Selection::Position {buffer_id, pos: usize::min(int.end, *param)})
+    monadic_rank1: |(param, _), buffer_id, int| Ok(
+        Selection::Position {buffer_id, pos: usize::min(int.end, *param)}
+    )
 }
 
-selection_function_param! {
-    name: character_sequential,
+selection_function_param!(
+    name: sequential_character,
     param_type: usize,
-    niladic: |(param, es): (usize, &EditorState)| {
-        let buf = get_buffer(es, es.current_buffer_id)?;
-        Ok(Selection::Position {
-            buffer_id: es.current_buffer_id,
-            pos: usize::min(param, buf.max_pos()),
-        })
-    },
+    niladic: |_| Err(SFError::NoNiladicForm(";n").into()),
     monadic_rank0: |(param, es), buffer_id, pos| {
         let buf = get_buffer(es, buffer_id)?;
         Ok(Selection::Position {buffer_id, pos: usize::min(pos+*param, buf.max_pos())})
@@ -35,4 +31,48 @@ selection_function_param! {
         let buf = get_buffer(es, buffer_id)?;
         Ok(Selection::Position {buffer_id, pos: usize::min(int.end+*param, buf.max_pos())})
     }
-}
+);
+
+selection_function_param!(
+    name: reverse_character,
+    param_type: usize,
+    niladic: |(param, es): (usize, &EditorState)| {
+        let buf = get_buffer(es, es.current_buffer_id)?;
+        Ok(Selection::Position {
+            buffer_id: es.current_buffer_id,
+            pos: if buf.max_pos() < param {
+                0
+            } else {
+                buf.max_pos() - param
+            },
+        })
+    },
+    monadic_rank0: |_, buffer_id, pos| Ok(Selection::Position {buffer_id, pos}),
+    monadic_rank1: |(param, _), buffer_id, int| Ok(
+        Selection::Position {buffer_id, pos: usize::min(int.end, *param)}
+    )
+);
+
+selection_function_param!(
+    name: sequential_reverse_character,
+    param_type: usize,
+    niladic: |_| Err(SFError::NoNiladicForm(";'n").into()),
+    monadic_rank0: |(param, _), buffer_id, pos| {
+        Ok(Selection::Position {buffer_id, pos: if *param<pos {pos - *param} else {0}})
+    },
+    monadic_rank1: |(param, _), buffer_id, int| {
+        Ok(Selection::Position {buffer_id, pos: if *param<int.end {int.end - *param} else {0}})
+    }
+);
+
+selection_function_param!(
+    name: reverse_sequential_character,
+    param_type: usize,
+    niladic: |_| Err(SFError::NoNiladicForm("';n").into()),
+    monadic_rank0: |(param, _), buffer_id, pos| {
+        Ok(Selection::Position {buffer_id, pos: if *param<pos {pos - *param} else {0}})
+    },
+    monadic_rank1: |(param, _), buffer_id, int| {
+        Ok(Selection::Position {buffer_id, pos: if *param<int.start {int.start - *param} else {0}})
+    }
+);
diff --git a/rprt-engine/src/selection_functions/function_end.rs b/rprt-engine/src/selection_functions/function_end.rs
index 47cff79..3f18fd3 100644
--- a/rprt-engine/src/selection_functions/function_end.rs
+++ b/rprt-engine/src/selection_functions/function_end.rs
@@ -4,14 +4,43 @@ use crate::selection_functions::types::{get_buffer, SFArguments, SFError, SFResu
 use crate::state::EditorState;
 
 selection_function! {
-    name: end_sequential,
+    name: end,
     niladic: |es: &EditorState| {
         let buf = get_buffer(es, es.current_buffer_id)?;
         Ok(Selection::Position {
             buffer_id: es.current_buffer_id,
-            pos: buf.max_pos()
+            pos: buf.max_pos(),
         })
     },
+    monadic_rank0: |_, buffer_id, pos | Ok(Selection::Position { buffer_id, pos }),
+    monadic_rank1: |_, buffer_id, int | Ok(Selection::Position { buffer_id, pos: int.end })
+}
+
+selection_function! {
+    name: reverse_end,
+    niladic: |es: &EditorState| {
+        Ok(Selection::Position {
+            buffer_id: es.current_buffer_id,
+            pos: 0,
+        })
+    },
+    monadic_rank0: |_, buffer_id, pos | Ok(Selection::Position { buffer_id, pos }),
+    monadic_rank1: |_, buffer_id, int | Ok(Selection::Position { buffer_id, pos: int.start })
+}
+
+selection_function! {
+    name: sequential_end,
+    niladic: |_| Err(SFError::NoNiladicForm(";$").into()),
+    monadic_rank0: |_, buffer_id, pos| Ok(Selection::Position { buffer_id, pos }),
+    monadic_rank1: |es, buffer_id, _| {
+        let buf = get_buffer(es, buffer_id)?;
+        Ok(Selection::Position { buffer_id, pos: buf.max_pos() })
+    }
+}
+
+selection_function! {
+    name: sequential_reverse_end,
+    niladic: |_| Err(SFError::NoNiladicForm(";'$").into()),
     monadic_rank0: |_, buffer_id, pos| {
         Ok(Selection::Position { buffer_id, pos })
     },
@@ -24,14 +53,15 @@ selection_function! {
 }
 
 selection_function! {
-    name: end_structural,
-    niladic: |es: &EditorState| {
-        let buf = get_buffer(es, es.current_buffer_id)?;
+    name: reverse_sequential_end,
+    niladic: |_| Err(SFError::NoNiladicForm("';$").into()),
+    monadic_rank0: |_, buffer_id, pos| {
+        Ok(Selection::Position { buffer_id, pos })
+    },
+    monadic_rank1: |_, buffer_id, interval| {
         Ok(Selection::Position {
-            buffer_id: es.current_buffer_id,
-            pos: buf.max_pos(),
+            buffer_id,
+            pos: interval.end,
         })
-    },
-    monadic_rank0: |_, buffer_id, pos | Ok(Selection::Position { buffer_id, pos }),
-    monadic_rank1: |_, buffer_id, int | Ok(Selection::Position { buffer_id, pos: int.end })
+    }
 }
diff --git a/rprt-engine/src/selection_functions/types.rs b/rprt-engine/src/selection_functions/types.rs
index 728d084..aaf0086 100644
--- a/rprt-engine/src/selection_functions/types.rs
+++ b/rprt-engine/src/selection_functions/types.rs
@@ -9,6 +9,8 @@ pub enum SFError {
     BufferNotFound(BufferID),
     #[error("Function {0} has no dyadic form")]
     NoDyadicForm(&'static str),
+    #[error("Function {0} has no dyadic form")]
+    NoNiladicForm(&'static str),
 }
 
 pub enum SFArguments<'a> {
@@ -59,7 +61,7 @@ macro_rules! selection_function_param {
     ) => {
         pub fn $name(param: $P, arg: SFArguments) -> SFResult {
             match arg {
-                SFArguments::Niladic { es } => $niladic_body((param, es)),
+                SFArguments::Niladic { es } => ($niladic_body)((param, es)),
                 SFArguments::Monadic { es, left } => {
                     left.vectorise(&(param, es), $monadic_rank0_body, $monadic_rank1_body)
                 }
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