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kotlinlang

how are `String`s represented in Kotlin, internally? as a sequence of bytes? (and if so, why can you not get a bytes array from a String in `O(1)` time?)
or is `String` a compiler builtin?

depends on the platform, but conceptually a `String` is a wrapper around an immutable `CharArray`

(on JVM, it's actually a `java.lang.String` at runtime, which has an internal `byte[]` representation, plus a bit to configure whether it's ISO-8859-1 or UTF-16 encoded)

to maintain immutability, to get a `ByteArray` it needs to make a copy either way

btw, a `Char` is a UTF-16 code unit. it is neither a byte nor a Unicode character

oh sorry, I see the definition of code unit now.

(possibly excessively pedantic) also, `String` doesn't validate that UTF-16 surrogates are properly paired either. in case it's not legal Unicode, a string may not be encodable to UTF-8 bytes