Enum DiscRow 

#[non_exhaustive]
pub enum DiscRow<'r> {
    I(&'r mut [i32]),
    F(&'r mut [f32]),
}

the summed row of a disc run: i32 x 4 per pixel, or f32 x 4 with DSF_F32

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

I(&'r mut [i32])

F(&'r mut [f32])