Whenever I see a DSL where part of the DSL's responsibility is to have arbitrarily complex mathematical expressions, my reactions are (a) why???, (b) well, if they're going to do it, they should have a formal language specification with a derived lexer and parser, and (c) the product needs a robust stdlib with compatibility across build targets.

From what I see in https://github.com/expo/exact/blob/main/contract/syntax/src/... and https://github.com/expo/exact/blob/main/contract/syntax/src/... - it's unclear this will scale to the levels of complexity that arbitrary UIs demand.