Introduction

Tezos smart contracts are written in Michelson, which is a stack-based language and the lowest level of language for a Tezos smart contract. Michelson code can be deployed as-is on the Tezos network.

However, if reading or writing Michelson code is still easy for small smart contracts, it can become tedious for more complex smart contracts, as:

• there are no variables and functions are not easy to use
• there is some syntactic sugar to combine multiple instructions but stack manipulation remains painful
• Michelson code cannot be broken down into several files
• stack-based languages are not commonly used when it comes to web development

LIGO offers an alternative.

It is a high-level language for smart contract development. Smart contracts can be written in LIGO, then compiled into a single Michelson code file. This Michelson file becomes the smart contract that will be deployed on a Tezos network.

FIGURE 1: Contextualization of LIGO in the Tezos ecosystem

LIGO currently offers two flavours of syntaxes:

• CameLigo, a syntax inspired from OCaml, that allows to write in a functional style.
• JsLigo, the latest syntax released, inspired by the popular JavaScript language.

Imperative programming is a programming paradigm that describes the operations in sequences of instructions executed by the computer to change the program's state.

Functional programming is a declarative programming paradigm that considers computation as an evaluation of mathematical functions.

Here is an example of a Counter contract that handles a single integer counter value in storage and allows users to increment, decrement or reset this counter.

CameLigo

type storage = int

type parameter =
  Increment of int
| Decrement of int
| Reset

type return = operation list * storage

// Two entrypoints

let add (store, delta : storage * int) : storage = store + delta
let sub (store, delta : storage * int) : storage = store - delta

(* Main access point that dispatches to the entrypoints according to
   the smart contract parameter. *)

let main (action, store : parameter * storage) : return =
 ([] : operation list),    // No operations
 (match action with
   Increment (n) -> add (store, n)
 | Decrement (n) -> sub (store, n)
 | Reset         -> 0)

JsLigo

type storage = int;

type parameter =
| ["Increment", int]
| ["Decrement", int]
| ["Reset"];

type return_ = [list <operation>, storage];

/* Two entrypoints */
const add = ([store, delta] : [storage, int]) : storage => store + delta;
const sub = ([store, delta] : [storage, int]) : storage => store - delta;

/* Main access point that dispatches to the entrypoints according to
   the smart contract parameter. */
const main = ([action, store] : [parameter, storage]) : return_ => {
 return [
   (list([]) as list <operation>),    // No operations
   (match (action, {
    Increment: (n: int) => add ([store, n]),
    Decrement: (n: int) => sub ([store, n]),
    Reset:     ()  => 0}))
  ]
};

What's next

In the following chapter, we will develop smart contracts in LIGO, compile them and deploy them.

We chose to write this module in JsLigo. The main difference between the syntax is that JsLigo is more imperative while CameLigo is more functional.

This module aims to teach developers the basics of LIGO by providing them with the essential skills to write and deploy their first smart contract onto the Tezos network. It will include the basics of the LIGO language, inspired from the official LIGO documentation, as well as detailed smart contract examples.