Primitive Types
Move has few built-in primitive types to represent numbers, addresses and boolean values: integers (u8, u64, u128), boolean
and address
.
Move does not have string type or floating point numbers.
Integer types
Integers are represented by u8
, u64
and u128
; Possible integer notations are:
script {
fun main() {
// define empty variable, set value later
let a: u8;
a = 10;
// define variable, set type
let a: u64 = 10;
// finally simple assignment
let a = 10;
// simple assignment with defined value type
let a = 10u128;
// in function calls or expressions you can use ints as constant values
if (a < 10) {};
// or like this, with type
if (a < 10u8) {}; // usually you don't need to specify type
}
}
Operator as
When you need to compare values or when function argument requires integer of different size you can cast your integer variable to another size by using operator as
:
script {
fun main() {
let a: u8 = 10;
let b: u64 = 100;
// we can only compare same size integers
if (a == (b as u8)) abort 11;
if ((a as u64) == b) abort 11;
}
}
Boolean
Boolean type is just the one you're used to. Two constant values: false
and true
- both can only mean one thing - a value of bool
type.
script {
fun main() {
// these are all the ways to do it
let b : bool; b = true;
let b : bool = true;
let b = true
let b = false; // here's an example with false
}
}
Address
Address is an identifier of sender (or wallet) in blockchain. The very basic operations which require address type are sending coins and importing modules.
script {
fun main() {
let addr: address; // type identifier
// in this book I'll use {{sender}} notation;
// always replace `{{sender}}` in examples with VM specific address!!!
addr = {{sender}};
// in Diem's Move VM - 16-byte address in HEX
addr = 0x...;
// in dfinance's DVM - bech32 encoded address with `wallet1` prefix
addr = wallet1....;
}
}