PS: I still prefer type 1 unums, due to their fallback to intervals :)
I'm very confused that you say posits are "more or less similar" to Binary Lambda Calculus. Posits are an inert data encoding: to interpret a posit as a number, we plug its parts (sign, regime, exponent and fraction) into a simple formula to get a numerical value. Those parts can have varying size (e.g. for soft posits), but the range of results is fundamentally limited by its use of exponentials.
In constrast, BLC is a Turing-complete, general-purpose programming language. To interpret a BLC value as a number, we:
- Parse its binary representation into lambda abstractions (00), function calls (01) and de-Bruijn-indexed variables (encoded in unary)
- Apply the resulting term to the symbol `one-more-than` and the symbol `zero`
- Beta-reduce that expression until it reaches a normal form. There is no way, in general, to figure out if this step will finish or get stuck forever: even if will eventually finish, that could take trillions of years or longer.
- Read the resulting symbols as a unary number, e.g. `one-more-than (one-more-than zero)` is the number two
Posit-style numbers can certainly be represented in BLC, by writing a lambda abstraction that implements the posit formula; but BLC can implement any other computable function, which includes many that grow much faster than the exponentials used in the posit formula (e.g. this has a nice explanation of many truly huge numbers https://www.reddit.com/r/math/comments/283298/how_to_compute... )