Pair / Tuple built-in type?

[AzizZayed]

I see that there are built-in types like Vec, Map and Set. Is there a pair or tuple built-in type? The usage would be like

(sort ITuple (Tuple i64 i64))
(sort SITuple (Tuple String i64))

[yihozhang]

Not currently! For now you have to write your own tuple datatype:

(datatype PairI64I64 (Pii i64 i64))
(function fst (Pairi64I64) i64)
(rule ((Pii a b)) ((set (fst (Pii a b)) a)))
...

Note that implementing pairs as built-in container types also has its limitations. For example, you cannot have (Pii a b) as part of the query if it's implemented as a built-in container.

[saulshanabrook]

Note that with user defined generics a pair type could be written more easily and re-used without having to redefine the rewrites for every type of pair: #386