Features
Smart Contracts

Introduction

Smart Contracts can be programmed using our own interpreted language running in a Virtual Machine, allowing safe and secure execution of code on the blockchain.

Smart Contracts are a way to automate the execution of a contract, without the need of a third party. They are self-executing contracts with the terms of the agreement directly written into lines of code.

A lot of use cases can be found for Smart Contracts, such as:

  • Decentralized applications (dApps)
  • Tokenization of assets
  • Voting systems
  • Supply chain management
  • etc.

Please note that they are not yet available on the mainnet, but are planned to be released in the future.

You can find the documentation of the XVM (opens in a new tab) below.

XELIS VM

XVM is an interpreted language developed in Rust. It supports constants, functions, while/foreach loops, arrays and structures. The syntax is strongly inspired by Rust and Golang.

All the verifications are mainly made at the level of the Parser to check the conformity of the code to be interpreted.

The different primitive types are:

  • byte (unsigned 8 bits integer)
  • short (unsigned 16 bits integer)
  • int (unsigned 64 bits integer)
  • long (unsigned 128 bits integer)
  • bool
  • string
  • struct

File extension is .xel

Documentation

the semicolon is optional, thus can be added if desired without any difference in the code.

Recursive functions are allowed, but limited to a configurable depth.

A environment system is completely customizable to set your own native functions. This helps to manage exactly what a program can interact with. Custom structs are also available.

Numbers

An error will be returned by the interpreter if an overflow is detected without causing a panic.

Rules

  • The value must be greater than or equal to 0.
  • You can put _ (underscore) for a better readability.
  • If no type is specified on the value, then int will be the default.

Examples

let my_byte: byte = 10
let my_short: short = 70
let my_int: int = 25655
let my_long: long = 100_000_000L

Variable

for constant variable, it must be declared outside a function, with const keyword.

Rules

  • Every variable must be declared with let or const keyword.
  • Variable name must alphanumeric characters.
  • Must provide value type.
  • If no value is set, null is set by default.

Examples

const hello: string = "hello"
...
let world: string = "world"

Casting

Values of built-in types can be casted into other built-in types easily using the keyword as.

Rules

  • Both value types must be a built-in type.

Examples

let id: long = 1337
let b: byte = id as byte
let id_str: string = id as string 

Function

entry function is a "public callable" function and must return a int value.

Rules

  • Must starts with func or entry keyword.
  • Signature is based on function name and parameters.
  • For type functions, the type must not be primitive.
  • Recursive functions are allowed.

Examples

entry foo() { ... }
func foo() { ... }
func foo(): int { ... }
func foo(a: int, b: int) { ... }
func (f Foo) bar() { ... }

Structure

A structure can contain other structures.

Rules

  • The name must be unique.
  • Name should start with a uppercase letter.
  • Only letters are allowed in name.
  • The last field does not need a comma.

Examples

struct MyStruct {
    message: string,
    value: int
}

Ternary

Rules

  • A bool condition is required.
  • The two values that can be returned must be of the same type.

Examples

let score: int = is_winner() ? 20 : 0

Negate operator

Rules

  • A bool condition is required after it.

Examples

let negative: bool = !condition

Array

Rules

  • All values must be of the same specified type.

Examples

let array: int[] = [10, 20, 30, 40]
...
let dim: int[][] = [[34, 17], [8, 14], [0, 69]]

If

Rules

  • Have a bool condition.

Examples

if condition {
	...
}
 
if (i > 20 && i != 25) || i == 0 {
	...
}

Else

Rules

  • It must be preceded by an if condition.

Examples

else {
	...
}

Else if

Rules

  • It must be preceded by an if or an else if condition.
  • Have a boolean condition.

Examples

else if condition {
	...
}
 
else if my_struct != null {
	...
}

While

Rules

  • Have a boolean condition.

Examples

while condition {
	...
}

Foreach

Rules

  • Have the name of a variable.
  • Have an array to go through

Examples

foreach val in values {
	...
}

For

Rules

  • Have the name of a variable.
  • Have a boolean condition.
  • Have an assign operator.

Examples

for i: int = 0; i < 10; i += 1 {
	...
}

Break

Rules

  • Must be in a loop (foreach, for, while).

Examples

while condition {
	if i % 10 == 0 {
		break;
	}
	...
}

Continue

Rules

  • Must be in a loop (foreach, for, while).

Examples

while condition {
	if i % 10 == 0 {
		continue;
	}
	...
}

Return

Rules

  • Must not have any code after.
  • If the function returns a value, the return must return a value.

Examples

func foo(): string {
	return "Hello World!"
}
 
func bar() {
	if condition {
		return
	}
	foo()
}

Scope

Allows you to isolate a part of the code / variables created.

Rules

  • No specific rules.

Examples

{
	...
}