theorem :: PARTFUN2:14

for C, D being non empty set
for f being PartFunc of C,D
for t being PartFunc of D,C st f is one-to-one & dom f = rng t & rng f = dom t & ( for c being Element of C
for d being Element of D st c in dom f & d in dom t holds
( f /. c = d iff t /. d = c ) ) holds
t = f "