let C be category; :: thesis:
assume A1: for o1, o2 being Object of C
for m being Morphism of o1,o2 holds
( m is retraction & <^o2,o1^> <> {} ) ; :: thesis:
A2: the carrier of (AllRetr C) = the carrier of AltCatStr(# the carrier of C, the Arrows of C, the Comp of C #) by Def3;
A3: the Arrows of (AllRetr C) cc= the Arrows of C by Def3;

now :: thesis:

let i be object ; :: thesis:
assume A4: i in [: the carrier of C, the carrier of C:] ; :: thesis:
then consider o1, o2 being object such that
A5: ( o1 in the carrier of C & o2 in the carrier of C ) and
A6: i = [o1,o2] by ZFMISC_1:84;
reconsider o1 = o1, o2 = o2 as Object of C by A5;
thus the Arrows of (AllRetr C) . i = the Arrows of C . i :: thesis:

proof

thus the Arrows of (AllRetr C) . i c= the Arrows of C . i by A2, A3, A4; :: according to XBOOLE_0:def 10 :: thesis:
let n be object ; :: according to TARSKI:def 3 :: thesis:
assume A7: n in the Arrows of C . i ; :: thesis:
then reconsider n1 = n as Morphism of o1,o2 by A6;
( <^o2,o1^> <> {} & n1 is retraction ) by A1;
then n in the Arrows of (AllRetr C) . (o1,o2) by A6, A7, Def3;
hence n in the Arrows of (AllRetr C) . i by A6; :: thesis:

end;

end;

hence AltCatStr(# the carrier of C, the Arrows of C, the Comp of C #) = AllRetr C by A2, ALTCAT_2:25, PBOOLE:3; :: thesis: