Account for missing floating point operations in core

See rust-lang/rfcs#2505 for details.

.build.yml

@@ -24,7 +24,7 @@ tasks:
       source $HOME/.cargo/env
       # Test with and without std
       cargo test
-      cargo test --no-default-features
+      cargo test --no-default-features --features libm
   # TODO: Add clippy and rustfmt lints. When doing that, make sure to add those
   # components to the rustup task above.
   - test-docs: |

Cargo.toml

@@ -28,8 +28,9 @@ linux-embedded-hal = "0.3"
 
 [features]
 default = ["std"]
-std = ["arrayvec/std"]
 examples = ["anyhow", "linux-embedded-hal", "std"]
+libm = ["num-traits/libm"]
+std = ["arrayvec/std", "num-traits/std"]
 
 [[example]]
 name = "true-frame-rate"

src/calculations.rs

@@ -54,6 +54,11 @@ use core::convert::TryInto;
 
 use embedded_hal::blocking::i2c;
 
+// Various floating point operations are not implemented in core, so we use libm to provide them as
+// needed.
+#[cfg_attr(feature = "std", allow(unused_imports))]
+use num_traits::Float;
+
 use crate::common::{Address, CalibrationData, MelexisCamera};
 use crate::register::Subpage;
 

src/lib.rs

@@ -110,6 +110,9 @@
 
 #![no_std]
 
+#[cfg(not(any(feature = "std", feature = "libm")))]
+compile_error!("Either the 'std' or 'libm' feature must be enabled.");
+
 pub mod calculations;
 pub mod common;
 pub mod driver;

src/mlx90640/eeprom.rs

@@ -5,6 +5,11 @@ use core::slice;
 use arrayvec::ArrayVec;
 use embedded_hal::blocking::i2c;
 
+// Various floating point operations are not implemented in core, so we use libm to provide them as
+// needed.
+#[cfg_attr(feature = "std", allow(unused_imports))]
+use num_traits::Float;
+
 use crate::common::*;
 use crate::error::{Error, LibraryError};
 use crate::expose_member;

src/mlx90640/mod.rs

@@ -3,12 +3,16 @@
 mod address;
 mod eeprom;
 
-pub use eeprom::Mlx90640Calibration;
+// Various floating point operations are not implemented in core, so we use libm to provide them as
+// needed.
+#[cfg_attr(feature = "std", allow(unused_imports))]
+use num_traits::Float;
 
 use crate::common::{Address, MelexisCamera, PixelAddressRange};
 use crate::register::{AccessPattern, Subpage};
 
 pub use address::RamAddress;
+pub use eeprom::Mlx90640Calibration;
 
 /// The height of the image captured by sensor in pixels.
 pub const HEIGHT: usize = 24;

src/mlx90641/eeprom.rs

@@ -8,6 +8,11 @@ use core::slice;
 use arrayvec::ArrayVec;
 use embedded_hal::blocking::i2c;
 
+// Various floating point operations are not implemented in core, so we use libm to provide them as
+// needed.
+#[cfg_attr(feature = "std", allow(unused_imports))]
+use num_traits::Float;
+
 use crate::common::*;
 use crate::error::{Error, LibraryError};
 use crate::expose_member;

src/mlx90641/mod.rs

@@ -4,6 +4,11 @@ mod address;
 mod eeprom;
 pub mod hamming;
 
+// Various floating point operations are not implemented in core, so we use libm to provide them as
+// needed.
+#[cfg_attr(feature = "std", allow(unused_imports))]
+use num_traits::Float;
+
 use core::cmp::Ordering;
 use core::iter;