Hi HN — I just published 0.1.0 of `connections`, a Rust port of an older Haskell library I wrote.

It's intended to address a common issue with casting: each cast's individual behavior is specified, but the syntax doesn’t describe what a cast and its reverse do together. Once several conversions are chained, their rounding, saturation, and range choices become difficult to reason about compositionally.

The core type packages a pair of monotone functions intended to satisfy a Galois law. A left connection, for example, has `ceil: A -> B` and `upper: B -> A`, with:

    ceil(a) <= b  iff  a <= upper(b)

A small example of the boundary behavior:

    use connections::conn::ConnR;
    use connections::core::u032::U032I032;

    assert_eq!(u32::MAX as i32, -1);
    assert_eq!(U032I032.floor(u32::MAX), i32::MAX);
    assert_eq!(U032I032.lower(-1), 0_u32);

    lower(b) <= a  iff  b <= floor(a)

0.1.0 includes families for Rust integers, IEEE floats, NonZero values, chars, sortable byte encodings, and IP/socket addresses, with optional Q-format, civil-time, hifitime, and hybrid-clock families. The default core has no third-party runtime dependencies; `Conn` is Copy, const-constructible, heap-free, and the crate forbids unsafe code.

Every included connection has a proptest law suite. Generated integer, Q-format, NonZero, and isomorphism families also have Kani harnesses over their full bit-width domains. The float claims are deliberately narrower and documented separately; floats use an N5 wrapper so NaN participates in an explicit reflexive preorder rather than being quietly excluded.

This isn’t intended to replace `TryFrom`: validation, runtime-parameterized conversions, and caller-selected policies generally belong in ordinary named functions.

Install:

    cargo add connections

I'd appreciate any feedback you can give me. Cheers!

Not sure I clear on usage.

In our code we use non byte numbers(deranged and arbitrary int crates), symmetric signed, ordered floats, new num type pattern, our const and categorical num traits(num-traits crate sucks), static assertions, prop tests, easy cast crate(sound as). We have custom decimals. And newtypes of u64 * u64 = u128.

Looking into lean4 provers integrated into rust).

Can your crate compose somewhat with above?