Answers.Body: <p>The simple answer is that tandem pawn notation is used, i.e., 18+1. This is not ambiguous because non-pawn pieces never use this notation since there can not be more than two of them, so if the first character is a number it means a pawn.</p>
  <p>While the rules technically might be a bit ambiguous there, I think it is clear what the intention of the rules are.</p>
  
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Answers.Text: Yes - this is another solution: always use integers when there are repeated pawns (two or more), and always use + and - when there are repeated non-pawns (two). But the rules (WXR) say to use + and - when there are two of any kind of piece, and there's no suggestion in 7.5 that they're using "piece" to mean "non-pawn", as is often the practice in international chess.
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Answers.Text: If you are talking about the "letter of the law" that is a valid point, but if you are interested in the spirit of it, then it should be very clear. There are 3 options: 1. Use a defined ambiguous notation, 2. Use a defined unambiguous notation, 3. Use an undefined notation. I think the answer suggests itself. Xiangqi rules often are more defined by examples than strict specifications, e.g., also for chasing rules, so interpreting it as "use as much disambiguation as necessary" seems very natural.
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Answers.Body: <p>I'm answering my own question here. If we want always to use four characters to denote a move, I suggest the following tweak to the rule for when two or more pieces on a file share a type:</p>
  <ul>
  <li><p><strong>Order all repeated pieces in that file.</strong> For example, if they are RCRCNN, number the rooks 1 and 3, the cannons 2 and 4, and the horses 5 and 6. If more than one piece type is repeated, do not use separate numberings for each type.</p>
  </li>
  <li><p>Use this number as the first character in the notation for the move.</p>
  </li>
  <li><p>Then apply normal rules for the second, third, and fourth characters.</p>
  </li>
  <li><p>Note that this requires using the file number as the second character. (Do not complicate things by using the piece type. We need to cope with positions where, for example, we have PRPR in file 4 and PCPC in file 7.)</p>
  </li>
  </ul>
  <p>Problem solved!</p>
  
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Body: <p>I've been reading the <a href="https://www.wxf-xiangqi.org/images/wxf-rules/2018_World_XiangQi_Rules_English2018.pdf" rel="nofollow noreferrer">World Xiangqi Rules</a> as approved by the World Xiangqi Federation and the Chinese Xiangqi Association, and in particular Article 7.5 which governs the notation for recording moves when there are two or more friendly pieces of the same type on the same file.</p>
  <p>The rule for this case is follows:</p>
  <ul>
  <li><p>a) if there are two such pieces, identify the moving piece as &quot;front&quot; (+) or &quot;rear&quot; (-), then give the piece type, and then proceed as normal to get the 3rd and 4th characters, e.g. +C=5 or +R+2;</p>
  </li>
  <li><p>b) if there are three or more such pieces (when they can only be pawns), identify the moving piece by order from the front, then give the file, and then again proceed as normal, e.g. 36=5.</p>
  </li>
  </ul>
  <p>But what if there are two files, each of which contains more than one pawn? For example, the position and move might be as shown here:</p>
  <p><a href="https://i.sstatic.net/5mWTAMHO.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/5mWTAMHO.jpg" alt="enter image description here" /></a></p>
  <p>Applying a) is what the rules tell us to do. This gives +P+1. Unfortunately, this would be ambiguous.</p>
  <p>Now an obvious thing to do would be to use b). This gives 18+1. Since the number of pawns on file 8 is only two, we could also, if we preferred, use a hybrid of a) and b) to get +8+1. Both 18+1 and +8+1 do the job.</p>
  <p>But whereas both 18+1 and +8+1 are unambiguous in the given position, both become ambiguous if we have a move and position like this one:</p>
  <p><a href="https://i.sstatic.net/XIwAqpUc.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/XIwAqpUc.jpg" alt="enter image description here" /></a></p>
  <p><strong>What is the standard notation for this move</strong>, used in games played under the WXR? (Or have I possibly found a hole in the rules?)</p>
  <p>If there isn't a standard WXR-competition answer to this question, what four-letter notation might reasonably be used for this move?</p>
  
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Comments.Text: What’s the notation rules when there aren’t multiple possibilities?
Comments.UserDisplayName: Laska
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Comments.CreationDate: 2024-07-25T02:34:31.940Z
Comments.Text: When you move a piece that's the only one of its type on its file, the rule is to identify the type, then the file, then say how the rank changes (+, -, or =), and then use the 4th character to identify either the destination file (if it's different from the file the piece is moving from) or to say how many spaces the piece has moved (if it's the same). This is considered somewhat infuriating by many, but combined with the rules that apply when the piece has one or more fellows on its file it has the beauty of always requiring exactly 4 characters. (Perhaps until this question? :-) )
Comments.UserDisplayName: tell
Tags: <xiangqi>
Title: Notation in Xiangqi when two files each contain two pieces of the same colour and type
ThreadText: # Notation in Xiangqi when two files each contain two pieces of the same colour and type
  
  (Asked by: username_0 on 2024-07-25)
  
  I've been reading the [World Xiangqi Rules](https://www.wxf-xiangqi.org/images/wxf-rules/2018_World_XiangQi_Rules_English2018.pdf) as approved by the World Xiangqi Federation and the Chinese Xiangqi Association, and in particular Article 7.5 which governs the notation for recording moves when there are two or more friendly pieces of the same type on the same file.
  
  The rule for this case is follows:
  
  * a) if there are two such pieces, identify the moving piece as "front" (+) or "rear" (-), then give the piece type, and then proceed as normal to get the 3rd and 4th characters, e.g. +C=5 or +R+2;
  * b) if there are three or more such pieces (when they can only be pawns), identify the moving piece by order from the front, then give the file, and then again proceed as normal, e.g. 36=5.
  
  But what if there are two files, each of which contains more than one pawn? For example, the position and move might be as shown here:
  
  [![enter image description here](https://i.sstatic.net/5mWTAMHO.jpg)](https://i.sstatic.net/5mWTAMHO.jpg)
  
  Applying a) is what the rules username_0 us to do. This gives +P+1. Unfortunately, this would be ambiguous.
  
  Now an obvious thing to do would be to use b). This gives 18+1. Since the number of pawns on file 8 is only two, we could also, if we preferred, use a hybrid of a) and b) to get +8+1. Both 18+1 and +8+1 do the job.
  
  But whereas both 18+1 and +8+1 are unambiguous in the given position, both become ambiguous if we have a move and position like this one:
  
  [![enter image description here](https://i.sstatic.net/XIwAqpUc.jpg)](https://i.sstatic.net/XIwAqpUc.jpg)
  
  **What is the standard notation for this move**, used in games played under the WXR? (Or have I possibly found a hole in the rules?)
  
  If there isn't a standard WXR-competition answer to this question, what four-letter notation might reasonably be used for this move?
  
  **Tags:** xiangqi
  
  > **Comments:**
  > **username_1**: What’s the notation rules when there aren’t multiple possibilities?  
  > **username_0**: When you move a piece that's the only one of its type on its file, the rule is to identify the type, then the file, then say how the rank changes (+, -, or =), and then use the 4th character to identify either the destination file (if it's different from the file the piece is moving from) or to say how many spaces the piece has moved (if it's the same). This is considered somewhat infuriating by many, but combined with the rules that apply when the piece has one or more fellows on its file it has the beauty of always requiring exactly 4 characters. (Perhaps until this question? :-) )  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_2 on 2024-07-25. Score: 0
  
  The simple answer is that tandem pawn notation is used, i.e., 18+1. This is not ambiguous because non-pawn pieces never use this notation since there can not be more than two of them, so if the first character is a number it means a pawn.
  
  While the rules technically might be a bit ambiguous there, I think it is clear what the intention of the rules are.
  
  > **Comments:**
  > **username_0**: Yes - this is another solution: always use integers when there are repeated pawns (two or more), and always use + and - when there are repeated non-pawns (two). But the rules (WXR) say to use + and - when there are two of any kind of piece, and there's no suggestion in 7.5 that they're using "piece" to mean "non-pawn", as is often the practice in international chess.  
  > **username_2**: If you are talking about the "letter of the law" that is a valid point, but if you are interested in the spirit of it, then it should be very clear. There are 3 options: 1. Use a defined ambiguous notation, 2. Use a defined unambiguous notation, 3. Use an undefined notation. I think the answer suggests itself. Xiangqi rules often are more defined by examples than strict specifications, e.g., also for chasing rules, so interpreting it as "use as much disambiguation as necessary" seems very natural.  
  
  ---
  
  ### Answer by username_0 on 2024-07-25. Score: 0
  
  I'm answering my own question here. If we want always to use four characters to denote a move, I suggest the following tweak to the rule for when two or more pieces on a file share a type:
  
  * **Order all repeated pieces in that file.** For example, if they are RCRCNN, number the rooks 1 and 3, the cannons 2 and 4, and the horses 5 and 6. If more than one piece type is repeated, do not use separate numberings for each type.
  * Use this number as the first character in the notation for the move.
  * Then apply normal rules for the second, third, and fourth characters.
  * Note that this requires using the file number as the second character. (Do not complicate things by using the piece type. We need to cope with positions where, for example, we have PRPR in file 4 and PCPC in file 7.)
  
  Problem solved!
  
  
  ---
  
  