1.9 KiB
Simplex.Messaging.Version
Version negotiation with proof-carrying compatibility checks.
Source: Version.hs
Overview
The module's central design: Compatible and VRange constructors are not exported. The only way to obtain a Compatible value is through the negotiation functions, and the only way to construct a VersionRange is through mkVersionRange (which validates) or parsing. This makes "compatibility was checked" a compile-time guarantee — code that holds a Compatible a has proof that negotiation succeeded.
See Simplex.Messaging.Version.Internal for why the Version constructor is separated.
mkVersionRange
Uses error if min > max. Safe only for compile-time constants. Runtime construction must use safeVersionRange, which returns Nothing on invalid input.
compatibleVersion vs compatibleVRange
compatibleVersion selects a single version: min(max1, max2) — the highest mutually-supported version. compatibleVRange returns the full intersection range: (max(min1,min2), min(max1,max2)). The intersection is used when both sides need to remember the agreed range for future version-gated behavior, not just the single negotiated version.
compatibleVRange'
Different from compatibleVRange: caps the range's maximum at a given version, rather than intersecting two ranges. Returns Nothing if the cap is below the range's minimum. Used when a peer reports a specific version and you need to constrain your range accordingly.
VersionI / VersionRangeI typeclasses
Allow extension types that wrap Version or VersionRange (e.g., types carrying additional handshake parameters alongside the version) to participate in negotiation without unwrapping. The associated types (VersionT, VersionRangeT) map between the version and range forms of the extension type.