Читать книгу Programming Kotlin Applications - Бретт Мак-Лахлин, Brett McLaughlin - Страница 58

Kotlin gives you four options for integers, largely varying based on range. These are shown in Table 2.1.

TABLE 2.1: Kotlin Types for Integers (Nondecimal Numbers)

TYPE	SIZE (BITS)	MINIMUM VALUE	MAXIMUM VALUE
Byte	8	–128	127
Short	16	–32,678	32,767
Int	32	–2,147,483,648 (–231)	2,147,483,647 (231 – 1)
Long	64	–9,223,372,036,854,775,808 (–263)	9,223,372,036,854,775,807 (263 – 1)

Kotlin will largely take care of figuring out which type to use when you don't declare that type explicitly. In that case, it's going to look at the value you're assigning the variable, and make some assumptions. This is a pretty important concept called type inference, and it's something we're going to talk about in a lot more detail in Chapter 6.

If you create a variable and assign it a number that fits into Int, then Int will be used. If the number is outside the range of Int, the variable will be created as a Long :

val someInt = 20 val tooBig = 4532145678

So here, someInt will be an Int. tooBig is too big to fit into an Int so it will be a Long. You can also force a variable to be a Long by adding a capital L to the value:

val makeItLong = 42L

Kotlin gives you a couple of options for decimals, as well: two, again, based on precision and size. Those are listed in Table 2.2.

TABLE 2.2: Kotlin Types for Decimal Numbers

TYPE	SIZE (BITS)	SIGNIFICANT BITS	EXPONENT BITS	DECIMAL DIGITS
Float	32	24	8	6–7
Double	64	53	11	15–16

Assignment here works a bit unexpectedly. Decimal variables will be Double unless you tell Kotlin to use Float by using the f or F suffix:

val g = 9.8 val theyAllFloat = 9.8F