theorem Th47: :: CGAMES_1:47

for g being ConwayGame holds
( g is zero iff ( ( for gL being ConwayGame holds
( not gL in the_LeftOptions_of g or gL is fuzzy or gL is negative ) ) & ( for gR being ConwayGame holds
( not gR in the_RightOptions_of g or gR is fuzzy or gR is positive ) ) ) ) by Th45;