@ikitommi What is the reason Malli use [:map [:x int?] [:y int?]] instead of [:map :x int? :y int?] ?

(I am asking for :map because I am wondering the same for :cat and :alt )

I guess that inside [:x int?] you can set many things: customized error message, validation function etc. Without vector[:x int?] expression structure becomes unreadable.

Good point.

I updated the tests for :cat and :alt . Those tests represent the proposal I make for the data format which constitutes the API for this part of Malli. Feedback welcome ! https://github.com/metosin/malli/pull/187/files