[GitHub] [lucenenet] NightOwl888 commented on a diff in pull request #654: fix: Aligned DeleteButSuffixFromElseReplace with Java code (FrenchStemmer.cs)

[GitBox <gi...@apache.org>]

NightOwl888 commented on code in PR #654:
URL: https://github.com/apache/lucenenet/pull/654#discussion_r995587910


##########
src/Lucene.Net.Analysis.Common/Analysis/Fr/FrenchStemmer.cs:
##########
@@ -483,21 +483,21 @@ private void DeleteButSuffixFromElseReplace(string source, string[] search, stri
                 {
                     if (source.EndsWith(prefix + search[i], StringComparison.Ordinal))
                     {
-                        sb.Remove(sb.Length - (prefix.Length + search[i].Length), sb.Length - sb.Length - (prefix.Length + search[i].Length));
+                        sb.Remove(sb.Length - (prefix.Length + search[i].Length), sb.Length);

Review Comment:
   The reason why this differs is because in Java the parameters are `startIndex` and `endIndex`, but in .NET we have `startIndex` and `length`. 
   
   https://docs.oracle.com/javase/8/docs/api/java/lang/StringBuilder.html#delete-int-int-
   https://learn.microsoft.com/en-us/dotnet/api/system.text.stringbuilder.remove?view=net-7.0
   
   Therefore, we need to do some light math to correct this:
   
   ```
   length = endIndex - startIndex
   ```
   
   This correction is common across many method conversions from Java to .NET.
   
   That being said, we are missing a set of parentheses here and in the other methods in this class to force the order of precedence, which is a very subtle bug:
   
   ```c#
   sb.Remove(sb.Length - (prefix.Length + search[i].Length), sb.Length - (sb.Length - (prefix.Length + search[i].Length)));
   ```



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