use std::ops::Add;
use std::ops::Div;
use num::{Zero, cast::AsPrimitive};

fn mean_impl<T, O, It, OUTPUT>(it: It) -> OUTPUT // OUTPUT::Output
where
    It: IntoIterator<Item = T>,
    T: Add<Output = O>,
    O: AsPrimitive<OUTPUT> + Zero + Add<T, Output = O>,
    OUTPUT: Copy + 'static + Div<Output = OUTPUT>,
    usize: AsPrimitive<OUTPUT>,
{
    let (count, total) = it
        .into_iter()
        .fold((0_usize, O::zero()), |(count, total), x| (count + 1, total + x));

    total.as_() / count.as_()
}

fn mean<T, O, It>(it: It) -> f64
where
    It: IntoIterator<Item = T>,
    T: Add<Output = O>,
    O: AsPrimitive<f64> + Zero + Add<T, Output = O>,
{
    mean_impl(it)
}

fn main() {
    dbg!(mean(&[1_i8,2,3,4,5,6]));
    dbg!(mean(&[1_u8,2,3,4,5,6]));
    dbg!(mean(&[1_i16,2,3,4,5,6]));
    dbg!(mean(&[1_u16,2,3,4,5,6]));
    dbg!(mean(&[1_i32,2,3,4,5,6]));
    dbg!(mean(&[1_u32,2,3,4,5,6]));
    dbg!(mean(&[1_i64,2,3,4,5,6]));
    dbg!(mean(&[1_u64,2,3,4,5,6]));
    dbg!(mean(&[1_f32,2.,3.,4.,5.,6.]));
    dbg!(mean(&[1_f64,2.,3.,4.,5.,6.]));
    dbg!(mean(vec![1_i8,2,3,4,5,6]));
    dbg!(mean(vec![1_u8,2,3,4,5,6]));
    dbg!(mean(vec![1_i16,2,3,4,5,6]));
    dbg!(mean(vec![1_u16,2,3,4,5,6]));
    dbg!(mean(vec![1_i32,2,3,4,5,6]));
    dbg!(mean(vec![1_u32,2,3,4,5,6]));
    dbg!(mean(vec![1_i64,2,3,4,5,6]));
    dbg!(mean(vec![1_u64,2,3,4,5,6]));
    dbg!(mean(vec![1_f32,2.,3.,4.,5.,6.]));
    dbg!(mean(vec![1_f64,2.,3.,4.,5.,6.]));
    //dbg!(mean(vec![1_f128,2.,3.,4.,5.,6.]));
}