From dcd930f855a22eabb2bbdf5ff6a041766189f686 Mon Sep 17 00:00:00 2001
From: Humza Shahid <humzasaur@gmail.com>
Date: Mon, 6 Oct 2025 17:08:57 +0100
Subject: [PATCH] begin expanding ? and + regex symbols, which we can represent
 using a combination of the others

---
 fcore/search-list/dfa-gen.sml | 120 ++++++++++++++++++++++++++++------
 1 file changed, 101 insertions(+), 19 deletions(-)

diff --git a/fcore/search-list/dfa-gen.sml b/fcore/search-list/dfa-gen.sml
index e4d7f0a..bcce534 100644
--- a/fcore/search-list/dfa-gen.sml
+++ b/fcore/search-list/dfa-gen.sml
@@ -10,6 +10,103 @@ struct
   | GROUP of regex
   | WILDCARD of int
 
+  fun incrementStates regex =
+    case regex of
+      CHAR_LITERAL {position, char} =>
+        let val i = position + 1
+        in (CHAR_LITERAL {position = i, char = char}, i)
+        end
+    | WILDCARD i => let val i = i + 1 in (WILDCARD i, i) end
+    | CONCAT {l, r, ...} =>
+        let
+          val (l, leftMaxState) = incrementStates l
+          val (r, rightMaxState) = incrementStates r
+          val concat = CONCAT
+            { l = l
+            , leftMaxState = leftMaxState
+            , r = r
+            , rightMaxState = rightMaxState
+            }
+        in
+          (concat, rightMaxState)
+        end
+    | ALTERNATION {l, r, ...} =>
+        let
+          val (l, leftMaxState) = incrementStates l
+          val (r, rightMaxState) = incrementStates r
+          val concat = ALTERNATION
+            { l = l
+            , leftMaxState = leftMaxState
+            , r = r
+            , rightMaxState = rightMaxState
+            }
+        in
+          (concat, rightMaxState)
+        end
+    | ZERO_OR_MORE child =>
+        let val (child, maxStates) = incrementStates child
+        in (ZERO_OR_MORE child, maxStates)
+        end
+    | _ => raise Fail "should not call increment on ? or +"
+
+  fun expandRegex regex =
+    case regex of
+      CHAR_LITERAL {position, ...} => (regex, position)
+    | WILDCARD i => (regex, i)
+    | CONCAT {l, r, leftMaxState, rightMaxState} =>
+        let
+          val (l, leftMaxState) = expandRegex l
+          val (r, rightMaxState) = expandRegex r
+          val node = CONCAT
+            { l = l
+            , r = r
+            , leftMaxState = leftMaxState
+            , rightMaxState = rightMaxState
+            }
+        in
+          (node, rightMaxState)
+        end
+    | ALTERNATION {l, r, leftMaxState, rightMaxState} =>
+        let
+          val (l, leftMaxState) = expandRegex l
+          val (r, rightMaxState) = expandRegex r
+          val node = ALTERNATION
+            { l = l
+            , r = r
+            , leftMaxState = leftMaxState
+            , rightMaxState = rightMaxState
+            }
+        in
+          (node, rightMaxState)
+        end
+    | GROUP regex =>
+        let val (regex, maxState) = expandRegex regex
+        in (GROUP regex, maxState)
+        end
+    | ZERO_OR_MORE regex =>
+        let val (regex, maxState) = expandRegex regex
+        in (ZERO_OR_MORE regex, maxState)
+        end
+
+    (* + symbol.
+     * We can expand this by constructing a concat, 
+     * putting the child in the concat's left,
+     * and an option Kleene star version of child on the right *)
+    | ONE_OR_MORE regex =>
+        let
+          val (l, leftMaxState) = expandRegex regex
+          val (r, rightMaxState) = incrementStates l
+          val r = ZERO_OR_MORE r
+          val node = CONCAT
+            { l = l
+            , leftMaxState = leftMaxState
+            , r = r
+            , rightMaxState = rightMaxState
+            }
+        in
+          (node, rightMaxState)
+        end
+
   structure Set =
   struct
     datatype 'a set = BRANCH of 'a set * int * 'a * 'a set | LEAF
@@ -350,26 +447,10 @@ struct
             else
               result
           end
-      | ZERO_OR_ONE child =>
-          getFollowsForPositionAndCharLoop (pos, regex, child, curChr)
+      | ZERO_OR_ONE _ =>
+          raise Fail "dfa-gen.sml 451: should expand so we don't have ?"
       | ONE_OR_MORE child =>
-          getFollowsForPositionAndCharLoop (pos, regex, child, curChr)
-
-    and getFollowsForPositionAndCharLoop (pos, regex, child, curChr) =
-      let
-        val result = getFollowsForPositionAndChar (child, pos, curChr)
-        val {sawConcat, follows, charIsMatch} = result
-      in
-        if charIsMatch then
-          if sawConcat then
-            result
-          else
-            let val fp = followpos (curChr, regex, follows)
-            in {sawConcat = false, follows = fp, charIsMatch = true}
-            end
-        else
-          result
-      end
+          raise Fail "dfa-gen.sml 451: should expand so we don't have +"
 
     fun getFollowPositionsFromList (lst: int list, regex, char, followSet) =
       case lst of
@@ -525,6 +606,7 @@ struct
     case ParseDfa.parse (str, 0) of
       SOME (ast, numStates) =>
         let
+          val (ast, numStates) = expandRegex ast
           val endMarker = CHAR_LITERAL {char = #"\^@", position = numStates + 1}
           val ast = CONCAT
             { l = ast