doc: Give crate feature flags its own doc page

Tighten up the crate feature list on the main page, and link over to a
page with more full information - where we can explain more. This gives
more room to the main page.

Author: bluss

src/doc/crate_feature_flags.rs

@@ -0,0 +1,35 @@
+//! Crate Feature Flags
+//!
+//! The following crate feature flags are available. They are configured in your
+//! `Cargo.toml` where the dependency on `ndarray` is defined.
+//!
+//! ## `std`
+//!   - Rust standard library (enabled by default)
+//!   - This crate can be used without the standard library by disabling the
+//!     default `std` feature. To do so, use `default-features = false` in
+//!     your `Cargo.toml`.
+//!   - The `geomspace` `linspace` `logspace` `range` `std` `var` `var_axis`
+//!     and `std_axis` methods are only available when `std` is enabled.
+//!
+//! ## `serde`
+//!   - Enables serialization support for serde 1.x
+//!
+//! ## `rayon`
+//!   - Enables parallel iterators, parallelized methods, the [`parallel`] module and [`par_azip!`].
+//!   - Implies std
+//!
+//! ## `approx`
+//!   - Enables implementations of traits from version 0.4 of the [`approx`] crate.
+//!
+//! ## `approx-0_5`
+//!   - Enables implementations of traits from version 0.5 of the [`approx`] crate.
+//!
+//! ## `blas`
+//!   - Enable transparent BLAS support for matrix multiplication.
+//!     Uses ``blas-src`` for pluggable backend, which needs to be configured
+//!     separately (see the README).
+//!
+//! ## `matrixmultiply-threading`
+//!   - Enable the ``threading`` feature in the matrixmultiply package
+//!
+//! [`parallel`]: crate::parallel

src/doc/mod.rs

@@ -1,3 +1,4 @@
 //! Standalone documentation pages.
 
+pub mod crate_feature_flags;
 pub mod ndarray_for_numpy_users;

src/lib.rs

@@ -75,30 +75,15 @@
 //! ## Crate Feature Flags
 //!
 //! The following crate feature flags are available. They are configured in your
-//! `Cargo.toml`.
+//! `Cargo.toml`. See [`doc::crate_feature_flags`] for more information.
 //!
-//! - `std`
-//!   - Rust standard library (enabled by default)
-//!   - This crate can be used without the standard library by disabling the
-//!     default `std` feature. To do so, use `default-features = false` in
-//!     your `Cargo.toml`.
-//!   - The `geomspace` `linspace` `logspace` `range` `std` `var` `var_axis`
-//!     and `std_axis` methods are only available when `std` is enabled.
-//! - `serde`
-//!   - Enables serialization support for serde 1.x
-//! - `rayon`
-//!   - Enables parallel iterators, parallelized methods, the [`parallel`] module and [`par_azip!`].
-//!   - Implies std
-//! - `approx`
-//!   - Enables implementations of traits from version 0.4 of the [`approx`] crate.
-//! - `approx-0_5`
-//!   - Enables implementations of traits from version 0.5 of the [`approx`] crate.
-//! - `blas`
-//!   - Enable transparent BLAS support for matrix multiplication.
-//!     Uses ``blas-src`` for pluggable backend, which needs to be configured
-//!     separately (see the README).
-//! - `matrixmultiply-threading`
-//!   - Enable the ``threading`` feature in the matrixmultiply package
+//! - `std`: Rust standard library-using functionality (enabled by default)
+//! - `serde`: serialization support for serde 1.x
+//! - `rayon`: Parallel iterators, parallelized methods, the [`parallel`] module and [`par_azip!`].
+//! - `approx` Implementations of traits from version 0.4 of the [`approx`] crate.
+//! - `approx-0_5`: Implementations of traits from version 0.5 of the [`approx`] crate.
+//! - `blas`: transparent BLAS support for matrix multiplication, needs configuration.
+//! - `matrixmultiply-threading`: Use threading from `matrixmultiply`.
 //!
 //! ## Documentation
 //!