Large numbers conversion to Byte in Kotlin

Question

Why does a double of 65555 converted to byte produce a result of 19 in Kotlin?

Answer 1

That's because of a numerical conversion from a wider type to a type of a smaller size. The Double (IEEE 754 double precision number) has its integral part factored to the powers of two as
65555 = 2¹⁷ + 2⁴ + 2² + 2⁰ = 65536 + 16 + 2 + 1, which is stored in binary form as (higher bits to lower):

 ‭... 0 1  0 0 0 0 0 0 0 0  0 0 0 1 0 0 1 1‬

When this number is converted to Byte, only its lowest 8 bits are retained:

 ... _ ‭_  _ _ _ _ _ _ _ _  0 0 0 1 0 0 1 1‬

And that results into 2⁴ + 2² + 2⁰ = 16 + 2 + 1 = 19.