RW wrote:IMO SE's forcing chains are in the end no different from the propositions made by gsf's program. Only difference is that SE has a nice way of showing the step by step path from the proposition to the contradiction. In fact, SE uses double propositions (nested forcing chains) to solve this puzzle, single propositions are not enough to solve it (unless there is some eliminations using UR, XY-wing or similar within the propositions).
you can use these options to see the results of propositions using all constraints
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-v2 -q+P-G
-v2 will show the basic constraints applied plus the proposition results
-v3 will show details of each proposition (P) with results
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D (deadend) contradiction
S solution
otherwise inconclusive
-q+P-G adds propositions to the constraints (+P) but disables guessing (-G) aka backtrack tree search
you can allow guessing to see how multi-tier propositions fare with -q+P (nested forcing chains)
the -v output models the constraints applied, not english, but the info is all there
this models the software architecture where new constraint methods are
easily added by assigning a constraint function to a letter -- all of the other
infrastructure comes for free, like constraint ordering, grouping, disabling, batching, stepping
use --man output to map constraint letters like FNBTHWXYPG to english names
if you like traditional player's forum position notation add
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-Fpr%rc%c -Fe= -Fn'<>'
or gurth's modified chess notation
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-Fp%kc%r
