Add the ability to run on no_std targets

Cargo.toml

@@ -16,16 +16,19 @@ bench = false
 test = true
 
 [dependencies]
-num-traits = ">=0.0.0"
-num-complex = ">=0.0.0"
+num-traits = { version = "0.2.9", default-features = false }
+num-complex = { version = "0.2.3", default-features = false }
 
 [dev-dependencies]
-rand = ">=0.7.0"
-rand_xorshift = ">=0.2.0"
+rand = "0.7.2"
+rand_xorshift = "0.2.0"
 
 [dev-dependencies.appro-eq]
-version=">=0.0.0"
+version= "0.3.0"
 features=["complex"]
 
 [features]
+default = ["std"]
 docs = []
+std = ["num-traits/std", "num-complex/std"]
+libm = ["num-traits/libm"]

src/cfft1d.rs

@@ -15,6 +15,9 @@ use num_traits::float::{Float, FloatConst};
 use num_traits::identities::{one, zero};
 use num_traits::{cast, NumAssign};
 
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
 #[derive(Debug)]
 enum WorkData<T> {
     MixedRadix(mixed_radix::MixedRadixData<T>),

src/cfft2d.rs

@@ -11,6 +11,9 @@ use num_traits::float::{Float, FloatConst};
 use num_traits::identities::{one, zero};
 use num_traits::{cast, NumAssign};
 
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
 /// Perform a complex-to-complex two-dimensional Fourier transform
 ///
 /// <script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS_CHTML"></script>

src/chirpz.rs

@@ -12,6 +12,9 @@ use num_traits::float::Float;
 use num_traits::identities::{one, zero};
 use num_traits::NumAssign;
 
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
 #[derive(Debug)]
 pub(crate) struct ChirpzData<T> {
     pub(crate) level: usize,

src/dct1d.rs

@@ -12,6 +12,9 @@ use num_traits::float::{Float, FloatConst};
 use num_traits::identities::{one, zero};
 use num_traits::{cast, NumAssign};
 
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
 /// Perform a discrete cosine transform
 ///
 /// # Example

src/lib.rs

@@ -1,4 +1,5 @@
 #![crate_type = "lib"]
+#![cfg_attr(not(feature = "std"), no_std)]
 
 //! Chalharu's Fastest Fourier Transform.
 //!
@@ -7,6 +8,13 @@
 //! version 2.0 (the "License"). You can obtain a copy of the License at
 //! http://mozilla.org/MPL/2.0/ .
 
+#[cfg(not(any(feature = "std", feature = "libm")))]
+compile_error!("Either feature 'std' or feature 'libm' must be enabled for 'chfft' to work");
+
+#[cfg(not(feature = "std"))]
+#[macro_use]
+extern crate alloc;
+
 mod chirpz;
 mod mixed_radix;
 mod precompute_utils;

src/mdct1d.rs

@@ -12,6 +12,9 @@ use num_traits::float::{Float, FloatConst};
 use num_traits::identities::zero;
 use num_traits::{cast, one, NumAssign};
 
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
 /// Perform a Modified discrete cosine transform
 ///
 /// <script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS_CHTML"></script>

src/mixed_radix.rs

@@ -12,6 +12,9 @@ use num_traits::float::{Float, FloatConst};
 use num_traits::identities::one;
 use num_traits::{cast, NumAssign};
 
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
 #[derive(Debug)]
 pub(crate) struct MixedRadixData<T> {
     pub(crate) ids: Vec<usize>,

src/precompute_utils.rs

@@ -10,14 +10,21 @@ use num_complex::Complex;
 use num_traits::cast;
 use num_traits::float::{Float, FloatConst};
 use num_traits::identities::one;
+
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+#[cfg(not(feature = "std"))]
+use core::cmp;
+#[cfg(feature = "std")]
 use std::cmp;
 
 #[inline]
 pub(crate) fn calc_omega_item<T: Float + FloatConst>(len: usize, position: usize) -> Complex<T> {
-    Complex::from_polar(
-        &one(),
-        &(cast::<_, T>(-2.0).unwrap() * T::PI() / cast(len).unwrap() * cast(position).unwrap()),
-    )
+    let r: T = one();
+    let theta: T =
+        cast::<_, T>(-2.0).unwrap() * T::PI() / cast(len).unwrap() * cast(position).unwrap();
+    // We can't use Complex::from_polar because it is at the time of writing not no_std compatible
+    Complex::new(r * theta.cos(), r * theta.sin())
 }
 
 // ωの事前計算

src/prime_factorization.rs

@@ -5,6 +5,9 @@
 //! version 2.0 (the "License"). You can obtain a copy of the License at
 //! http://mozilla.org/MPL/2.0/ .
 
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
 #[derive(Debug)]
 pub(crate) struct Factor {
     pub(crate) value: usize,

src/rfft1d.rs

@@ -12,6 +12,9 @@ use num_traits::float::{Float, FloatConst};
 use num_traits::identities::{one, zero};
 use num_traits::{cast, NumAssign};
 
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
 /// Perform a real-to-complex one-dimensional Fourier transform
 ///
 /// <script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS_CHTML"></script>