Function conditional_copy_float_to 

pub fn conditional_copy_float_to<T: Copy + 'static>(
    mask: &BooleanArray<()>,
    then_data: &[T],
    else_data: &[T],
    output: &mut [T],
)

Zero-allocation variant: writes directly to caller’s output buffer.

Conditional copy for floating-point arrays with runtime type dispatch. Panics if output.len() != mask.len.