movedblackpieceecho.cql

// Download movedblackpieceecho.cql
// PGN output when run on sample.pgn

/*************
Pairs of positions with the source in the mainline and the target
in the variations. They differ only in that
a single black piece has moved. They are reached by a path from
their latest common ancestor that has at least 15 consecutive
identical moves. (A "Warning: truncating long comment" warning when running
this file can be ignored).
The output is sorted by the number of consecutive moves
************/

cql(input hhdbvi.pgn variations)
 mainline
 sort "consecutive identical moves"
  echo (source target){
   variation
   sidetomove==source:sidetomove
   try
   mismatches= ~(source∩target)
   #mismatches==2
   ◭Mover=▲∩mismatches
   ∀x∊mismatches
     x==Mover and source:(x∩□)
         or
     x∩□ and source:(x==Mover)
   ///Mover " moved from " source:Mover
   consecutivemoves (source target)≥15
 }