Variables & Reactivity

Basic Declaration

In FLIN, you declare variables without any keywords:

variables.flin

name = "Juste"       // text (inferred)
count = 0              // int
price = 99.99          // float
active = true          // bool
items = []             // empty list

💡 No let, const, or var

FLIN doesn't use declaration keywords. All variables are mutable and reactive by default.

Automatic Reactivity

When a variable changes, the UI updates automatically:

app/index.flin

name = "World"

<input value={name} input={name = event.value} />
<p>Hello, {name}!</p>

When you type in the input, the paragraph updates instantly. No setState, no dispatch.

Type Annotations

Types are inferred, but you can be explicit:

typed-variables.flin

score: float = 0
tags: [text] = []
user: User? = none      // optional
point: (int, int) = (10, 20)  // tuple

Built-in Types

Type	Example	Description
`text`	`"hello"`	UTF-8 string
`int`	`42`	64-bit integer
`float`	`3.14`	64-bit float
`bool`	`true`	Boolean
`time`	`now`	UTC timestamp
`[T]`	`[1, 2, 3]`	List
`T?`	`none`	Optional

⚠ Important

FLIN uses text (not string), int (not integer), and none (not null or undefined).