Handicap 2 Popeye
Code by Alain Brobecker, sample problem by Jacques Dupin
This small tool creates a Popeye file to test a "handicap" proofgame from a given position in Forsyth notation in which one side has given a piece as handicap, but we don't know which side and which piece. So it is using the by using the a=>b stipulation and processes all possible start positions using the next command. The tool removes useless tests for unmoved pawns (eg: 12 unmoved pawns), pawns moved one step with unmoved neigbours (eg d3 and c6), unmoveable bishops (eg: f1,c8,f8) and caged rooks still there in the end position (eg h1,a8,h8).

PG Forsyth:
Handicap style:
W/B piece     W piece     B piece
W/B pawn     W pawn     B pawn
W/B officer     W officer     B officer


If you're interested in chess proof games, retrograde analysis and computing, see also:
The retrograde analysis corner by Otto Janko
Chess Problem Database
Popeye by many authors
Jacobi and chess problems by computer by François Labelle
Natch and iNatch by Pascal Wassong
Euclide by Etienne Dupuis
Retractor by Chad Whipkey and Theodore Hwa
The retro mailing list
The website of Václav Kotesovec
The website of Andrew Buchanan
The website of Eric Angelini

My own page with chess problems