Working with no-std

Cargo.toml

@@ -11,7 +11,7 @@ keywords = ["ann", "knn", "nearest-neighbors"]
 categories = ["algorithms", "data-structures"]
 
 [dependencies]
-num-traits = "0.2.14"
+num-traits = { version = "0.2.14", default-features = false }
 
 [dev-dependencies]
 criterion = "0.3.5"

src/coords.rs

@@ -1,5 +1,6 @@
 //! [Coordinate spaces](https://en.wikipedia.org/wiki/Cartesian_coordinate_system).
 
+use alloc::vec::Vec;
 use crate::distance::Value;
 
 /// A coordinate space.

src/cos.rs

@@ -6,7 +6,7 @@ use crate::distance::{Distance, Metric, Proximity, Value};
 use num_traits::real::Real;
 use num_traits::{one, zero};
 
-use std::cmp::Ordering;
+use core::cmp::Ordering;
 
 /// Compute the [cosine *similarity*] between two points.
 ///
@@ -436,7 +436,7 @@ macro_rules! impl_distance {
 
             #[inline]
             fn try_from(value: $f) -> Result<Self, Self::Error> {
-                if value >= 0.0 && value <= std::$f::consts::PI {
+                if value >= 0.0 && value <= core::$f::consts::PI {
                     Ok(Self(value.cos()))
                 } else {
                     Err(InvalidAngleError)
@@ -492,7 +492,7 @@ impl_distance!(f64);
 mod tests {
     use super::*;
 
-    use std::f64::consts::{FRAC_PI_2, FRAC_PI_4, PI, SQRT_2};
+    use core::f64::consts::{FRAC_PI_2, FRAC_PI_4, PI, SQRT_2};
 
     #[test]
     fn test_cosine() {

src/euclid.rs

@@ -4,9 +4,10 @@
 use crate::distance::{Distance, Metric, Proximity, Value};
 use crate::lp::Minkowski;
 
+use num_traits::real::Real;
 use num_traits::zero;
 
-use std::cmp::Ordering;
+use core::cmp::Ordering;
 
 /// A point in Euclidean space.
 ///

src/exhaustive.rs

@@ -2,6 +2,7 @@
 
 use crate::distance::Proximity;
 use crate::knn::{ExactNeighbors, NearestNeighbors, Neighborhood};
+use alloc::vec::Vec;
 
 /// A [`NearestNeighbors`] implementation that does exhaustive search.
 #[derive(Clone, Debug)]
@@ -48,7 +49,7 @@ impl<T> FromIterator<T> for ExhaustiveSearch<T> {
 
 /// An iterator that moves values out of an exhaustive index.
 #[derive(Debug)]
-pub struct IntoIter<T>(std::vec::IntoIter<T>);
+pub struct IntoIter<T>(alloc::vec::IntoIter<T>);
 
 impl<T> Iterator for IntoIter<T> {
     type Item = T;
@@ -69,7 +70,7 @@ impl<T> IntoIterator for ExhaustiveSearch<T> {
 
 /// An iterator over the values in an exhaustive index.
 #[derive(Debug)]
-pub struct Iter<'a, T>(std::slice::Iter<'a, T>);
+pub struct Iter<'a, T>(core::slice::Iter<'a, T>);
 
 impl<'a, T> Iterator for Iter<'a, T> {
     type Item = &'a T;

src/kd.rs

@@ -6,6 +6,10 @@ use crate::lp::Minkowski;
 use crate::knn::{ExactNeighbors, NearestNeighbors, Neighborhood};
 use crate::util::Ordered;
 
+use alloc::vec;
+use alloc::vec::Vec;
+use alloc::boxed::Box;
+
 use num_traits::Signed;
 
 /// A node in a k-d tree.
@@ -467,7 +471,7 @@ impl<T: Coordinates> FromIterator<T> for FlatKdTree<T> {
 
 /// An iterator that moves values out of a flat k-d tree.
 #[derive(Debug)]
-pub struct FlatIntoIter<T>(std::vec::IntoIter<FlatKdNode<T>>);
+pub struct FlatIntoIter<T>(vec::IntoIter<FlatKdNode<T>>);
 
 impl<T> Iterator for FlatIntoIter<T> {
     type Item = T;
@@ -488,7 +492,7 @@ impl<T> IntoIterator for FlatKdTree<T> {
 
 /// An iterator over the values in a flat k-d tree.
 #[derive(Debug)]
-pub struct FlatIter<'a, T>(std::slice::Iter<'a, FlatKdNode<T>>);
+pub struct FlatIter<'a, T>(core::slice::Iter<'a, FlatKdNode<T>>);
 
 impl<'a, T> Iterator for FlatIter<'a, T> {
     type Item = &'a T;

src/knn.rs

@@ -1,5 +1,6 @@
 //! [Nearest neighbor search](https://en.wikipedia.org/wiki/Nearest_neighbor_search) interfaces.
 
+use alloc::vec::Vec;
 use crate::distance::{Distance, Proximity};
 
 /// A nearest neighbor.

src/lib.rs

@@ -122,7 +122,10 @@
 //! [`k_nearest_within()`]: knn::NearestNeighbors#method.k_nearest_within
 //! [`ExactNeighbors`]: knn::ExactNeighbors
 
-#![warn(rust_2018_idioms)]
+#![no_std]
+
+#[macro_use]
+extern crate alloc;
 
 pub mod chebyshev;
 pub mod coords;

src/util.rs

@@ -1,6 +1,6 @@
 //! Internal utilities.
 
-use std::cmp::Ordering;
+use core::cmp::Ordering;
 
 /// A wrapper that converts a partial ordering into a total one by panicking.
 #[derive(Clone, Copy, Debug, PartialOrd)]

src/vp.rs

@@ -4,9 +4,13 @@ use crate::distance::{Distance, DistanceValue, Metric, Proximity};
 use crate::knn::{ExactNeighbors, NearestNeighbors, Neighborhood};
 use crate::util::Ordered;
 
+use alloc::boxed::Box;
+use alloc::vec;
+use alloc::vec::Vec;
+
 use num_traits::zero;
 
-use std::fmt::{self, Debug, Formatter};
+use core::fmt::{self, Debug, Formatter};
 
 /// A node in a VP tree.
 #[derive(Debug)]
@@ -527,7 +531,7 @@ impl<T: Proximity> FromIterator<T> for FlatVpTree<T> {
 }
 
 /// An iterator that moves values out of a flat VP tree.
-pub struct FlatIntoIter<T: Proximity>(std::vec::IntoIter<FlatVpNode<T>>);
+pub struct FlatIntoIter<T: Proximity>(vec::IntoIter<FlatVpNode<T>>);
 
 impl<T> Debug for FlatIntoIter<T>
 where
@@ -559,7 +563,7 @@ impl<T: Proximity> IntoIterator for FlatVpTree<T> {
 }
 
 /// An iterator over the values in a flat VP tree.
-pub struct FlatIter<'a, T: Proximity>(std::slice::Iter<'a, FlatVpNode<T>>);
+pub struct FlatIter<'a, T: Proximity>(core::slice::Iter<'a, FlatVpNode<T>>);
 
 impl<'a, T> Debug for FlatIter<'a, T>
 where