From 44c2fbb3c73a295699e185e22871d2e4dcaad58a Mon Sep 17 00:00:00 2001
From: Humza Shahid <humzasaur@gmail.com>
Date: Tue, 7 Oct 2025 09:48:10 +0100
Subject: [PATCH] handle character ranges like a-z in character class and
 negated character class

---
 fcore/search-list/dfa-gen.sml | 30 +++++++++++++++++++++++++++++-
 temp.txt                      |  4 +---
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/fcore/search-list/dfa-gen.sml b/fcore/search-list/dfa-gen.sml
index c5f2c58..483ef54 100644
--- a/fcore/search-list/dfa-gen.sml
+++ b/fcore/search-list/dfa-gen.sml
@@ -126,6 +126,7 @@ struct
       | #"|" => (true, chr)
       | #"?" => (true, chr)
       | #"." => (true, chr)
+      | #"-" => (true, chr)
       (* standard escape sequences *)
       | #"a" => (true, #"\a")
       | #"b" => (true, #"\b")
@@ -138,6 +139,17 @@ struct
       | #"\"" => (true, chr)
       | _ => (false, chr)
 
+    fun getCharsBetween (lowChr, highChr, acc) =
+      if lowChr = highChr then
+        highChr :: acc
+      else
+        let
+          val acc = lowChr :: acc
+          val lowChr = Char.succ lowChr
+        in
+          getCharsBetween (lowChr, highChr, acc)
+        end
+
     fun getCharsInBrackets (pos, str, acc) =
       if pos = String.size str then
         NONE
@@ -159,7 +171,23 @@ struct
             let val chars = Vector.fromList acc
             in SOME (pos + 1, chars)
             end
-        | chr => getCharsInBrackets (pos + 1, str, chr :: acc)
+        | #"-" => NONE
+        | chr =>
+            if
+              pos + 1 < String.size str andalso String.sub (str, pos + 1) = #"-"
+              andalso pos + 2 < String.size str
+            then
+              (* handle character ranges like a-z *)
+              let
+                val chr2 = String.sub (str, pos + 2)
+                val lowChr = if chr < chr2 then chr else chr2
+                val highChr = if chr > chr2 then chr else chr2
+                val acc = getCharsBetween (lowChr, highChr, acc)
+              in
+                getCharsInBrackets (pos + 3, str, acc)
+              end
+            else
+              getCharsInBrackets (pos + 1, str, chr :: acc)
 
     fun parseCharacterClass (pos, str, stateNum) =
       case getCharsInBrackets (pos, str, []) of
diff --git a/temp.txt b/temp.txt
index c550179..ad50577 100644
--- a/temp.txt
+++ b/temp.txt
@@ -1,3 +1 @@
-hello(
-fellow
-yellow
+abcdefghijklmnopqrstuvwxyz + - * /