Variables

Variables

Variables allow NXL programs to store values.

A declaration looks like:

let age = 23
let name = "Tanmoy"

The interpreter evaluates the initializer, creates a runtime value, and stores it in the environment.

Conceptually:

"Tanmoy"
    ↓
Value::String
    ↓
Environment
    ↓
name → "Tanmoy"

Variable lookup

When NXL evaluates:

print(name)

the interpreter performs the equivalent of:

Identifier("name")
        ↓
Environment.get("name")
        ↓
Value::String("Tanmoy")

Assignment

The environment also has an assign() operation.

The intended behavior is:

let age = 23
age = 24

This updates the existing variable.

Scopes

NXL uses environments to represent scopes.

let x = 10

if true {
    let x = 20
    print(x)
}

print(x)

Conceptually:

Global
│
├── x = 10
│
└── If Block
    │
    └── x = 20

Inside the block, x refers to 20; outside, it refers to 10.

Parent environments allow nested scopes to find values from outer scopes.