When I try to type the following Michelson script, I get a type error.

parameter unit;
storage (big_map (pair string address) (list timestamp));
code {CDR; NIL operation; PAIR};
Ill formed type.
At line 2 characters 17 to 37,
comparable type expected.Type pair string address is not comparable.

According to the Michelson reference, types pair ty1 ty2, address, and string are comparable. Am I missing something? Is there are way to circumvent this issue?

1 Answer 1


This feature is not totally implemented in Babylon (http://tezos.gitlab.io/protocols/006_carthage.html#comparable-pairs-in-sets-and-maps), but it will arrive with Cartage in a few days if the vote is stakeholders vote for it. You can follow the election of Carthage at this address : https://tzstats.com/election/16


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