iterstats 0.7.0

Statistics for rust iterators.
Documentation 
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//! Replace NANs with something else.

use num_traits::Float;

use crate::Iterstats;

/// Fill NAN values with a replacement.
pub trait FillNan<A = Self>: Sized {
    /// The output type.
    type Output;

    /// Replace NANs & get a new iterator.
    fn fill_nan<I: Iterator<Item = A>>(
        iter: I,
        repl: Self::Output,
    ) -> FillNanIter<impl Iterator<Item = Self::Output>, Self::Output>;
}

/// Struct returned by [`FillNan`].
#[derive(Debug, Clone, Copy)]
pub struct FillNanIter<I, A> {
    /// The iterator to replace NANs in.
    iter: I,
    /// The value to use as the replacement
    repl: A,
}

impl<I, A> Iterator for FillNanIter<I, A>
where
    I: Iterator<Item = A>,
    A: Float,
{
    type Item = A;

    fn next(&mut self) -> Option<Self::Item> {
        self.iter
            .next()
            .map(|item| if item.is_nan() { self.repl } else { item })
    }
}

macro_rules! fillnan_impl {
    ($typ:ty) => {
        impl FillNan for $typ {
            type Output = $typ;

            fn fill_nan<I: Iterator<Item = Self>>(
                iter: I,
                repl: Self::Output,
            ) -> FillNanIter<impl Iterator<Item = Self::Output>, Self::Output> {
                FillNanIter { iter, repl }
            }
        }

        impl FillNan for &$typ {
            type Output = $typ;

            fn fill_nan<I: Iterator<Item = Self>>(
                iter: I,
                repl: Self::Output,
            ) -> FillNanIter<impl Iterator<Item = Self::Output>, Self::Output> {
                iter.map(|i| *i).fill_nan(repl)
            }
        }
    };
}

fillnan_impl!(f64);
fillnan_impl!(f32);

#[cfg(test)]
mod tests {
    use super::*;
    use paste::paste;

    macro_rules! test_fillnan {
        ($name:ident: $typ:ty as $iter:expr; into_iter => $repl:literal $expected:expr) => {
            paste! {
                #[test]
                fn [<$name _into_iter>]() {
                    let filled = <$typ>::fill_nan($iter.into_iter(), $repl).collect::<Vec<_>>();
                    assert_eq!(filled, $expected);
                }
            }
        };
        ($name:ident: $typ:ty as $iter:expr; iter => $repl:literal $expected:expr) => {
            paste! {
                #[test]
                fn [<$name _iter>]() {
                    let filled = <&$typ>::fill_nan($iter.iter(), $repl).collect::<Vec<_>>();
                    assert_eq!(filled, $expected);
                }
            }
        };
        ($name:ident: $typ:ty as $iter:expr => $repl:literal $expected:expr) => {
            test_fillnan!($name: $typ as $iter; iter => $repl $expected);
            test_fillnan!($name: $typ as $iter; into_iter => $repl $expected);
        };
    }

    test_fillnan!(f64: f64 as [0.1, -2.3, f64::NAN, f64::INFINITY, 2.1] => 0. vec![0.1, -2.3, 0.0, f64::INFINITY, 2.1]);
    test_fillnan!(f32: f32 as [0.1, -2.3, f32::NAN, f32::INFINITY, 2.1] => 0. vec![0.1, -2.3, 0.0, f32::INFINITY, 2.1]);
}