chameleon-echo.cql; chameleon-echo.cql can be downloaded here.
; Chameleon echoes: positions that have an echo by a shifted version, ; with the color of square on which each piece in the source is on ; changing in the target. Output is sorted by the number of ; pieces which must be at least 4. Note: this code runs slowly, so by default only ; game 1 1000 are evaluated (you can use --gamenumber to override this) ; Note that the numberment to npieces must come after the relation, so ; that it is only matched when the relation also matches. Otherwise, ; the sorting will take into account the number of pieces in positions ; that do not match the relation cql(input heijden.pgn gamenumber 1 1000) K on lightsquares relation K on darksquares (tomove match) echoshift (mismatch 0) sort "Number of pieces" countsquares 4 32 [Aa]