Feature Flags

Each crate supports std and alloc feature gates for no_std compatibility.

Default Features

By default, all crates enable std:

karpal-core = "0.7"  # enables std by default

karpal-core = { version = "0.7", default-features = false, features = ["alloc"] }

Core traits work without any allocator:

karpal-core = { version = "0.7", default-features = false }

Crate	Feature	Effect
`karpal-verify`	`amari`	Statistical verification via amari-flynn
`karpal-proof`	`derive`	`#[derive(VerifySemigroup)]` etc.
`karpal-verify`	`derive`	`#[export_obligations]` macro

Crate	`no_std` (core only)	`alloc`	`std`	Notes
`karpal-core`	✅	✅	✅	HKT encoding, functor hierarchy, Semigroup/Monoid work without alloc
`karpal-profunctor`	✅	✅	✅	Profunctor, Strong, Choice, FnP
`karpal-optics`	✅	✅	✅	Lens, Prism, composition
`karpal-arrow`	✅	✅	✅	Arrow hierarchy
`karpal-free`	✅	✅	✅	Free constructions (alloc required for most)
`karpal-recursion`	✅	✅	✅	Recursion schemes
`karpal-algebra`	✅	✅	✅	Abstract algebra
`karpal-effect`	✅	✅	✅	Monad transformers
`karpal-proof`	✅	✅	✅	Law witnesses, refinement types
`karpal-verify`	❌	❌	✅	Verification bridge (process spawning, filesystem)
`karpal-verify-derive`	❌	❌	✅	Proc-macro crate (requires std)
`karpal-proof-derive`	❌	❌	✅	Proc-macro crate (requires std)
`karpal-diagram`	✅	✅	✅	String diagrams
`karpal-schubert-types`	❌	❌	✅	Depends on `amari-enumerative`
`karpal-higher`	✅	✅	✅	2-categories, enriched categories
`karpal-std`	❌	❌	✅	Prelude re-exports (pulls in all crates)

CI verifies this via cargo build --no-default-features -p karpal-core -p karpal-profunctor on every push.