ligo/gitlab-pages/docs/language-basics/boolean-if-else.md

id	title
boolean-if-else	Boolean, If, Else

Boolean

The type of a Boolean is bool and the possible values are True and False.

Here's how to define a boolean:

const a: bool = True;
const b: bool = False;

let a: bool = true
let b: bool = false

let a: bool = true;
let b: bool = false;

Comparing two values

In LIGO, only values of the same type can be compared. We call these "comparable types." Comparable types include e.g. int, nat, string, tez, timestamp, address, ...

Comparing strings

const a: string = "Alice";
const b: string = "Alice";
// True
const c: bool = (a = b);

let a: string = "Alice"
let b: string = "Alice"
// true
let c: bool = (a = b)

let a: string = "Alice";
let b: string = "Alice";
// true
let c: bool = (a == b);

Comparing numbers

const a: int = 5;
const b: int = 4;
const c: bool = (a = b);
const d: bool = (a > b);
const e: bool = (a < b);
const f: bool = (a <= b);
const g: bool = (a >= b);
const h: bool = (a =/= b);

let a: int = 5
let b: int = 4
let c: bool = (a = b)
let d: bool = (a > b)
let e: bool = (a < b)
let f: bool = (a <= b)
let g: bool = (a >= b)
let h: bool = (a =/= b)

let a: int = 5;
let b: int = 4;
let c: bool = (a == b);
let d: bool = (a > b);
let e: bool = (a < b);
let f: bool = (a <= b);
let g: bool = (a >= b);
let h: bool = (a != b);

Comparing tez

💡 Comparing tez values is especially useful when dealing with an amount sent in a transaction.

const a: tez = 5mutez;
const b: tez = 10mutez;
const c: bool = (a = b);

let a: tez = 5mutez
let b: tez = 10mutez
// false
let c: bool = (a = b)

let a: tez = 5mutez;
let b: tez = 10mutez;
// false
let c: bool = (a == b);

Conditionals, if staments, and more

Conditional logic is an important part of every real world program.

If/else statements

const min_age: nat = 16n;

(*
    This function is really obnoxious, but it showcases
    how the if statement and it's syntax can be used.

    Normally, you'd use `with (age > min_age)` instead.
*)
function is_adult(const age: nat): bool is
    block {
        var is_adult: bool := False;
        if (age > min_age) then begin
            is_adult := True;
        end else begin
            is_adult := False;
        end
    } with is_adult

You can run the function above with

ligo run-function -s pascaligo src/if-else.ligo is_adult 21n

let min_age: nat = 16n

(**

    This function is really obnoxious, but it showcases
    how the if statement and it's syntax can be used.

    Normally, you'd use `with (age > min_age)` instead.

*)
let is_adult (age: nat) : bool =
  if (age > min_age) then true else false

let min_age: nat = 16n;

/**

    This function is really obnoxious, but it showcases
    how the if statement and it's syntax can be used.

    Normally, you'd use `with (age > min_age)` instead.

*/

let is_adult = (age: nat): bool =>
  if (age > min_age) {
    true;
  } else {
    false;
  };

You can run the function above with

ligo run-function -s cameligo src/if-else.mligo is_adult 21n