add support for no_std

Cargo.toml

@@ -14,8 +14,12 @@ documentation = "https://docs.rs/fixed"
 repository = "https://gitlab.com/tspiteri/fixed"
 readme = "README.md"
 keywords = ["mathematics", "numerics"]
-categories = ["algorithms", "data-structures", "science"]
+categories = ["algorithms", "data-structures", "no-std", "science"]
 license = "MIT/Apache-2.0"
 
 [dependencies]
 typenum = "1.3"
+
+[features]
+default = ["std"]
+std = []

README.md

@@ -35,6 +35,10 @@ fixed-point numbers.
 
 ## What’s new
 
+### Version 0.1.2 news (unreleased)
+
+  * The crate can now be used without the standard library `std`.
+
 ### Version 0.1.1 news (2018-08-11)
 
   * Comparisons are now supported between all fixed-point numbers with
@@ -103,6 +107,24 @@ You also need to declare it by adding this to your crate root (usually
 extern crate fixed;
 ```
 
+## Optional features
+
+The *fixed* crate has one optional features:
+
+ 1. `std`, enabled by default. This adds a dependency on the standard
+    library `std`. Currently this makes no difference functionally,
+    but that may change in the future.
+
+The `std` feature is enabled by default; to use the crate without a
+dependency on the standard library `std`, you can add the dependency
+like this to [*Cargo.toml*]:
+
+```toml
+[dependencies.fixed]
+version = "0.1.1"
+default-features = false
+```
+
 ## License
 
 This crate is free software: you can redistribute it and/or modify it

RELEASES.md

@@ -5,6 +5,11 @@ modification, are permitted in any medium without royalty provided the
 copyright notice and this notice are preserved. This file is offered
 as-is, without any warranty. -->
 
+Version 0.1.2 (unreleased)
+==========================
+
+  * The crate can now be used without the standard library `std`.
+
 Version 0.1.1 (2018-08-11)
 ==========================
 

src/arith.rs

@@ -13,14 +13,14 @@
 // <https://www.apache.org/licenses/LICENSE-2.0> and
 // <https://opensource.org/licenses/MIT>.
 
-use frac::Unsigned;
-use std::cmp::Ordering;
-use std::iter::{Product, Sum};
-use std::mem;
-use std::ops::{
+use core::cmp::Ordering;
+use core::iter::{Product, Sum};
+use core::mem;
+use core::ops::{
     Add, AddAssign, BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign, Div, DivAssign,
     Mul, MulAssign, Neg, Not, Rem, RemAssign, Shl, ShlAssign, Shr, ShrAssign, Sub, SubAssign,
 };
+use frac::Unsigned;
 use {
     FixedHelper, FixedI128, FixedI16, FixedI32, FixedI64, FixedI8, FixedU128, FixedU16, FixedU32,
     FixedU64, FixedU8,

src/cmp.rs

@@ -13,8 +13,8 @@
 // <https://www.apache.org/licenses/LICENSE-2.0> and
 // <https://opensource.org/licenses/MIT>.
 
+use core::cmp::Ordering;
 use frac::{self, Unsigned};
-use std::cmp::Ordering;
 use {
     FixedI128, FixedI16, FixedI32, FixedI64, FixedI8, FixedU128, FixedU16, FixedU32, FixedU64,
     FixedU8,
@@ -135,7 +135,7 @@ mod tests {
 
     #[test]
     fn cmp_signed() {
-        use std::cmp::Ordering::*;
+        use core::cmp::Ordering::*;
         let neg1_16 = FixedI32::<frac::U16>::from_int(-1).unwrap();
         let neg1_20 = FixedI32::<frac::U20>::from_int(-1).unwrap();
         let mut a = neg1_16;
@@ -172,7 +172,7 @@ mod tests {
 
     #[test]
     fn cmp_unsigned() {
-        use std::cmp::Ordering::*;
+        use core::cmp::Ordering::*;
         let one_16 = FixedU32::<frac::U16>::from_int(1).unwrap();
         let one_20 = FixedU32::<frac::U20>::from_int(1).unwrap();
         let mut a = one_16;

src/display.rs

@@ -13,9 +13,11 @@
 // <https://www.apache.org/licenses/LICENSE-2.0> and
 // <https://opensource.org/licenses/MIT>.
 
-use std::cmp::Ordering;
-use std::fmt::{Binary, Debug, Display, Formatter, LowerHex, Octal, Result as FmtResult, UpperHex};
-use std::str;
+use core::cmp::Ordering;
+use core::fmt::{
+    Binary, Debug, Display, Formatter, LowerHex, Octal, Result as FmtResult, UpperHex,
+};
+use core::str;
 use typenum::Unsigned;
 use FixedHelper;
 
@@ -158,6 +160,7 @@ fn dec_int_digits(int_bits: u32) -> u32 {
     let digits = (int_bits * 3 + i) / 10;
 
     // check that digits is ceil(log10(2^int_bits - 1)), except when int_bits < 2
+    #[cfg(feature = "std")]
     debug_assert!(
         int_bits < 2 || digits == (f64::from(int_bits).exp2() - 1.0).log10().ceil() as u32
     );
@@ -179,8 +182,10 @@ fn dec_frac_digits(frac_bits: u32) -> u32 {
     // check that error < delta, where
     // error = 0.5 * 10^-digits
     // delta = 2^-frac_bits
+    #[cfg(feature = "std")]
     debug_assert!(0.5 * 10f64.powi(0 - digits as i32) < (-f64::from(frac_bits)).exp2());
     // check that error with one less digit >= delta
+    #[cfg(feature = "std")]
     debug_assert!(0.5 * 10f64.powi(1 - digits as i32) >= (-f64::from(frac_bits)).exp2());
 
     digits
@@ -272,7 +277,7 @@ where
     fmt.pad_integral(!is_neg, "", buf)
 }
 
-#[cfg(test)]
+#[cfg(all(test, feature = "std"))]
 mod tests {
     use *;
 
@@ -304,7 +309,6 @@ mod tests {
             let bits = !0u32 ^ i;
             let flt = bits as f64 / (frac as f64).exp2();
             let fix = FixedU32::<Frac>::from_bits(bits);
-            println!("i is {}", i);
             assert_eq!(format!("{}", fix), format!("{:.2}", flt));
         }
     }

src/helper.rs

@@ -13,9 +13,8 @@
 // <https://www.apache.org/licenses/LICENSE-2.0> and
 // <https://opensource.org/licenses/MIT>.
 
-use std::cmp::Ordering;
-use std::mem;
-
+use core::cmp::Ordering;
+use core::mem;
 use typenum::Unsigned;
 use {
     FixedI128, FixedI16, FixedI32, FixedI64, FixedI8, FixedU128, FixedU16, FixedU32, FixedU64,

src/lib.rs

@@ -75,6 +75,24 @@ You also need to declare it by adding this to your crate root (usually
 extern crate fixed;
 ```
 
+## Optional features
+
+The *fixed* crate has one optional features:
+
+ 1. `std`, enabled by default. This adds a dependency on the standard
+    library `std`. Currently this makes no difference functionally,
+    but that may change in the future.
+
+The `std` feature is enabled by default; to use the crate without a
+dependency on the standard library `std`, you can add the dependency
+like this to [*Cargo.toml*]:
+
+```toml
+[dependencies.fixed]
+version = "0.1.1"
+default-features = false
+```
+
 ## License
 
 This crate is free software: you can redistribute it and/or modify it
@@ -110,11 +128,15 @@ additional terms or conditions.
 [channels]: https://doc.rust-lang.org/book/second-edition/appendix-07-nightly-rust.html
 [const generics]: https://github.com/rust-lang/rust/issues/44580
 */
+#![cfg_attr(not(feature = "std"), no_std)]
 #![warn(missing_docs)]
 #![doc(html_root_url = "https://docs.rs/fixed/0.1.1")]
 #![doc(test(attr(deny(warnings))))]
 #![cfg_attr(nightly_repr_transparent, feature(repr_transparent))]
 
+#[cfg(feature = "std")]
+extern crate core;
+
 extern crate typenum;
 
 macro_rules! if_signed {
@@ -139,13 +161,13 @@ pub mod frac;
 mod helper;
 
 use arith::MulDivDir;
+use core::cmp::Ordering;
+use core::f32;
+use core::f64;
+use core::hash::{Hash, Hasher};
+use core::marker::PhantomData;
 use frac::Unsigned;
 use helper::FixedHelper;
-use std::cmp::Ordering;
-use std::f32;
-use std::f64;
-use std::hash::{Hash, Hasher};
-use std::marker::PhantomData;
 
 macro_rules! pass_method {
     ($comment:expr, $Fixed:ident($Inner:ty) => fn $method:ident()) => {