Chapter 7 : Conditionals


Booleans are typed bool in LIGO :

let a: bool = true; // or false

Comparing Values

Only values of the same type can be natively compared, i.e. int, nat, string, tez, timestamp, address, etc… However some values of the same type are not natively comparable, i.e. maps, sets or lists. You will have to write your own comparison functions for those.

// Comparing strings

let a: string = “Alice”;

let b: string = “Alice”;

let c: bool = (a == b); // true

// Comparing numbers

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

let a: tez = 5 as mutez;

let b: tez = 10 as mutez;

let c: bool = (a == b); // false


Conditional logic enables forking the control flow depending on the state.

let isSmall = (n : nat) : bool => {  if (n < (10 as nat)) { return true; } else { return false; };};

Your mission

We want to conditionally change the engine attribute (third number) to 1 only if it is equal to 0.

1- Refactor modified_ship as a variable equal to my_ship

2- Then define a condition if the engine attribute equal 0. Don’t forget the attributes are defined as strings.

3- If the condition is met, change modified_ship to it new value. Otherwise, skip the instructions.

⚠️ If you have installed LIGO then you can test the execution of the modify_ship function by running the following command:

ligo run-function main.ligo modify_ship '("010433")'