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Constants & Variables

The next building block after types are constants and variables.

Constants

Constants are immutable by design, which means their values can't be reassigned. When defining a constant you need to provide a name, type and a value:

const age : int = 25;

You can evaluate the constant definition above using the following CLI command:

ligo evaluate-value -s pascaligo gitlab-pages/docs/language-basics/src/variables-and-constants/const.ligo age
# Outputs: 25
let age: int = 25

You can evaluate the constant definition above using the following CLI command:

ligo evaluate-value -s cameligo gitlab-pages/docs/language-basics/src/variables-and-constants/const.mligo age
# Outputs: 25

Variables

Variables, unlike constants, are mutable. They can't be used in a global scope, but they can be used within functions, or function arguments.

💡 Don't worry if you don't understand the function syntax yet. We'll get to it in upcoming sections of the docs.

// won't work, use const for global values instead
// var four: int = 4;

function add(const a: int; const b: int) : int is
    block { 
        var c : int := a + b;
     } with c

⚠️ Notice the different assignment operator :=

You can run the add function defined above using the LIGO compiler like this:

ligo run-function -s pascaligo gitlab-pages/docs/language-basics/src/variables-and-constants/add.ligo add '(1,1)' 
# Outputs: 2

As expected from a functional language, CameLIGO uses value-binding for variables rather than assignment. Variables are changed by replacement, with a new value being bound in place of the old one.

💡 Don't worry if you don't understand the function syntax yet. We'll get to it in upcoming sections of the docs.


let add(const a: int; const b: int) : int =
  let c : int = a + b in c

You can run the add function defined above using the LIGO compiler like this:

ligo run-function -s cameligo gitlab-pages/docs/language-basics/src/variables-and-constants/add.mligo add '(1,1)' 
# Outputs: 2
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