mbeckerle commented on code in PR #1435:
URL: https://github.com/apache/daffodil/pull/1435#discussion_r1956507677


##########
daffodil-runtime1/src/main/scala/org/apache/daffodil/runtime1/processors/dfa/CreateDelimiterDFA.scala:
##########
@@ -186,26 +186,33 @@ object CreateDelimiterDFA {
   private def buildTransitions(
     nextState: DelimStateBase,
     delim: Seq[DelimBase],
-    allStates: ArrayBuffer[State],
+    allStates: Array[State],
     ignoreCase: Boolean
   ): State = {
 
-    if (delim.isEmpty && nextState != null) {
-      // We are initial state
-      nextState.stateName = "StartState" // "PTERM0"
-      return nextState
+    var i = 0
+    var remainingDelim = delim
+    var currentNextState = nextState
+
+    while (remainingDelim.nonEmpty) {
+      val currentState = getState(
+        remainingDelim.head,
+        if (currentNextState == null) DFA.FinalState else 
currentNextState.stateNum,
+        remainingDelim.length - 1,
+        allStates,
+        ignoreCase
+      )
+      remainingDelim = remainingDelim.tail
+      allStates(i) = currentState
+      currentNextState = currentState
+      i += 1
     }
 
-    val currentState = getState(
-      delim(0),
-      if (nextState == null) DFA.FinalState else nextState.stateNum,
-      delim.length - 1,
-      allStates,
-      ignoreCase
-    )
-    val rest = delim.tail
+    if (currentNextState != null) {
+      // We are initial state
+      currentNextState.stateName = "StartState" // "PTERM0"
+    }
 
-    allStates += currentState
-    return buildTransitions(currentState, rest, allStates, ignoreCase)

Review Comment:
   So this was tail recursive, but you rewrote it as iterative. Why? 
   
   I'm ok with the rewrite. We try to avoid functional style overheads in the 
runtime1 part of daffodil. This little mini compiler of delimiters is very old 
code before we settled on while-loops as the main thing for runtime1. 
   
   I just didn't expect to see such a revision in a PR that is about 2.13/3.x 
conversion. 
   
   



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