Interpreter

Interpreter

The interpreter is the execution engine.

It takes the AST and evaluates it:

Program
   │
   ▼
Statement
   │
   ▼
Expression
   │
   ▼
Runtime Value

Variable declaration

For:

let name = "Tanmoy"

the interpreter:

1. Evaluates "Tanmoy".
2. Creates a runtime Value.
3. Stores it in the environment.

Conceptually:

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

Variable lookup

For:

print(name)

the interpreter evaluates:

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

Built-in print()

NXL currently has one built-in function:

print("Hello")

The parser creates:

Call
├── callee: print
└── arguments:
    └── "Hello"

The interpreter recognizes print as a built-in, evaluates its argument, and sends it to stdout.

For:

print(23)

the output is:

23

Current runtime

The interpreter currently understands:

• variable declarations
• literal values
• variable lookup
• expression statements
• blocks
• print()

The AST and parser already contain more functionality than the interpreter currently executes. This is intentional: the architecture allows language features to be implemented incrementally.