no_std & Embedded

rustebra is no_std by default: src/lib.rs declares #![cfg_attr(not(test), no_std)], so the crate has no dependency on the standard library (outside test builds) and no allocator requirement unless you opt in.

Without any feature flags, only stack-allocated, compile-time-sized types are available: StaticVector<T, N> and StaticMatrix<T, R, C>, whose lengths/shapes are const generics. These work on embedded targets with no heap at all.

Enabling the alloc feature pulls in extern crate alloc and unlocks heap-allocated, runtime-sized types: DynamicVector<T>, DynamicMatrix<T>, and every sparse matrix type in rustebra::sparse (CooMatrix, CsrMatrix, CscMatrix, and their sorted variants), all of which are gated behind #[cfg(feature = "alloc")] and simply don’t exist in the crate’s public API without it.

# no_std, no allocator: only StaticVector/StaticMatrix are available.
[dependencies]
rustebra = "0.3"

# adds DynamicVector/DynamicMatrix and the sparse module.
[dependencies]
rustebra = { version = "0.3", features = ["alloc"] }

Gotchas

• Code that references DynamicVector, DynamicMatrix, or anything in rustebra::sparse without the alloc feature enabled won’t compile — these items aren’t hidden behind a runtime check, they’re absent from the crate entirely.
• StaticMatrix::determinant on matrices larger than 4x4 returns Err(DeterminantError::MatrixTooLargeWithoutAlloc) when the alloc feature is disabled — cofactor expansion beyond that size needs heap-allocated scratch space that isn’t available in a pure no_std build.