more no_std support

Cargo.toml

@@ -24,6 +24,7 @@ test = false
 
 [dependencies]
 either = { version = "1.0", default-features = false }
+hashbrown = { version = "0.8", optional = true}
 
 [dev-dependencies]
 rand = "0.7"
@@ -38,6 +39,7 @@ version = "0.2"
 
 [features]
 default = ["use_std"]
+use_alloc = ["hashbrown"]
 use_std = []
 
 [profile]

src/adaptors/mod.rs

@@ -11,7 +11,6 @@ pub use self::coalesce::*;
 pub use self::map::{map_into, map_ok, MapInto, MapOk};
 #[allow(deprecated)]
 pub use self::map::MapResults;
-#[cfg(feature = "use_std")]
 pub use self::multi_product::*;
 
 use std::fmt;

src/adaptors/multi_product.rs

@@ -1,5 +1,5 @@
-#![cfg(feature = "use_std")]
 
+use crate::lib::Vec;
 use crate::size_hint;
 use crate::Itertools;
 

src/combinations.rs

@@ -1,4 +1,5 @@
 use std::fmt;
+use crate::lib::Vec;
 
 use super::lazy_buffer::LazyBuffer;
 

src/combinations_with_replacement.rs

@@ -1,5 +1,9 @@
 use std::fmt;
 
+#[cfg(not(feature = "use_std"))]
+use crate::lib::vec;
+use crate::lib::Vec;
+
 use super::lazy_buffer::LazyBuffer;
 
 /// An iterator to iterate through all the `n`-length combinations in an iterator, with replacement.

src/free.rs

@@ -3,11 +3,11 @@
 //! The benefit of free functions is that they accept any `IntoIterator` as
 //! argument, so the resulting code may be easier to read.
 
+#[cfg(feature = "use_std")]
+use crate::VecIntoIter;
 #[cfg(feature = "use_std")]
 use std::fmt::Display;
 use std::iter::{self, Zip};
-#[cfg(feature = "use_std")]
-type VecIntoIter<T> = ::std::vec::IntoIter<T>;
 
 #[cfg(feature = "use_std")]
 use crate::Itertools;
@@ -17,13 +17,11 @@ pub use crate::adaptors::{
     merge,
     put_back,
 };
-#[cfg(feature = "use_std")]
 pub use crate::put_back_n_impl::put_back_n;
 #[cfg(feature = "use_std")]
 pub use crate::multipeek_impl::multipeek;
 #[cfg(feature = "use_std")]
 pub use crate::peek_nth::peek_nth;
-#[cfg(feature = "use_std")]
 pub use crate::kmerge_impl::kmerge;
 pub use crate::zip_eq_impl::zip_eq;
 pub use crate::merge_join::merge_join_by;

src/group_map.rs

@@ -1,6 +1,5 @@
-#![cfg(feature = "use_std")]
 
-use std::collections::HashMap;
+use crate::lib::{HashMap, Vec};
 use std::hash::Hash;
 use std::iter::Iterator;
 
@@ -21,6 +20,7 @@ pub fn into_group_map<I, K, V>(iter: I) -> HashMap<K, Vec<V>>
     lookup
 }
 
+#[cfg(feature = "use_std")]
 pub fn into_group_map_by<I, K, V>(iter: I, f: impl Fn(&V) -> K) -> HashMap<K, Vec<V>>
     where
         I: Iterator<Item=V>,

src/groupbylazy.rs

@@ -1,5 +1,5 @@
 use std::cell::{Cell, RefCell};
-use std::vec;
+use crate::lib::{vec, Vec};
 
 /// A trait to unify FnMut for GroupBy with the chunk key in IntoChunks
 trait KeyFunction<A> {

src/kmerge_impl.rs

@@ -1,5 +1,6 @@
 use crate::size_hint;
 use crate::Itertools;
+use crate::lib::Vec;
 
 use std::mem::replace;
 use std::fmt;

src/lazy_buffer.rs

@@ -1,4 +1,5 @@
 use std::ops::Index;
+use crate::lib::Vec;
 
 #[derive(Debug, Clone)]
 pub struct LazyBuffer<I: Iterator> {