Add std feature.

Cargo.toml

@@ -17,6 +17,7 @@ keywords = [
 	"welzl-algorithm",
 ]
 categories = [
+	"no-std",
 	"science",
 	"graphics",
 	"algorithms",
@@ -31,9 +32,20 @@ include = [
 	"LICENSES/*",
 ]
 
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
 [dependencies]
+nalgebra = { version = "0.32.4", default-features = false, features = ["alloc"] }
+stacker = { version = "0.1.15", optional = true }
+
+[features]
+default = ["std"]
+std = ["dep:stacker"]
+
+[dev-dependencies]
 nalgebra = { version = "0.32.4", features = ["rand"] }
-stacker = "0.1.15"
 
 [profile.test]
 opt-level = 2

RELEASES.md

@@ -2,6 +2,7 @@
 
   * Lower trait bounds on `Ball` and `Enclosing`.
   * Use `T` in favor of `R` as does `nalgebra`.
+  * Allow `no_std` by gating `stacker` dependency and `Deque` implementations behind `std` feature.
 
 # Version 0.3.0 (2024-03-17)
 

src/deque.rs

@@ -4,6 +4,7 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
+#[cfg(feature = "std")]
 use std::collections::{LinkedList, VecDeque};
 
 /// Minimum double-ended queue interface.
@@ -29,6 +30,7 @@ pub trait Deque<T> {
 	}
 }
 
+#[cfg(feature = "std")]
 impl<T> Deque<T> for VecDeque<T> {
 	#[inline]
 	fn len(&self) -> usize {
@@ -54,6 +56,7 @@ impl<T> Deque<T> for VecDeque<T> {
 	}
 }
 
+#[cfg(feature = "std")]
 impl<T> Deque<T> for LinkedList<T> {
 	#[inline]
 	fn len(&self) -> usize {

src/enclosing.rs

@@ -5,12 +5,19 @@
 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
 use super::{Deque, OVec};
+use core::mem::size_of;
 use nalgebra::{
 	base::allocator::Allocator, DefaultAllocator, DimName, DimNameAdd, DimNameSum, OPoint,
 	RealField, U1,
 };
+#[cfg(feature = "std")]
 use stacker::maybe_grow;
-use std::mem::size_of;
+
+#[cfg(not(feature = "std"))]
+#[inline]
+fn maybe_grow<R, F: FnOnce() -> R>(_red_zone: usize, _stack_size: usize, callback: F) -> R {
+	callback()
+}
 
 /// Minimum enclosing ball.
 pub trait Enclosing<T: RealField, D: DimName>
@@ -72,15 +79,17 @@ where
 	/// to the front and enclosed ones to the back.
 	///
 	/// Implements [Welzl's recursive algorithm] with move-to-front heuristic. No allocations happen
-	/// unless real field `T` is not [`Copy`] or stack size enters dimension-dependant red zone in
-	/// which case temporary stack space will be allocated.
+	/// unless the real field `T` is not [`Copy`] or the stack size enters the dimension-dependant
+	/// red zone in which case temporary stack space will be allocated on the heap if the `std`
+	/// feature is enabled.
 	///
 	/// [Welzl's recursive algorithm]: https://api.semanticscholar.org/CorpusID:17569809
 	///
 	/// # Complexity
 	///
-	/// Expected time complexity is *O*(*n*) for *n* randomly permuted points. Complexity constant
-	/// *c* as in *cn* is significantly reduced by reusing permuted points of previous invocations.
+	/// Expected time complexity is *O*((*n*+1)(*n*+1)!*m*) for *m* randomly permuted
+	/// *n*-dimensional points. The complexity constant in *m* is significantly reduced by reusing
+	/// permuted points of previous invocations.
 	///
 	/// # Example
 	///

src/lib.rs

@@ -14,10 +14,17 @@
 //!   * Find minimum enclosing *n*-ball of *n*-balls.
 //!   * Find minimum-volume enclosing *n*-ellipsoid.
 //!   * Improve numerical stability and performance.
+//!
+//! # Features
+//!
+//!   * `std` for spilling recursion stack over to the heap if necessary. Enabled by `default`.
 
-#![forbid(missing_docs)]
 #![forbid(unsafe_code)]
+#![forbid(missing_docs)]
+#![forbid(rustdoc::broken_intra_doc_links)]
 #![allow(clippy::tabs_in_doc_comments)]
+#![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(docsrs, feature(doc_auto_cfg))]
 
 mod ball;
 mod deque;

src/ovec.rs

@@ -4,8 +4,8 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
+use core::mem::take;
 use nalgebra::{base::allocator::Allocator, DefaultAllocator, DimName, OVector};
-use std::mem::take;
 
 /// Owned vector of item `T` and capacity `D`.
 #[doc(hidden)]