# 2. Variables & Types

## Declaring variables
Use `let` to create a variable. Reassign without `let`.
```stencil
let name = "Ember";
let age = 20;
age = 21;            // reassign
print(name, age);    // Ember 21
```
`mut` and `var` are accepted as synonyms of `let`:
```stencil
mut score = 0;
score = score + 10;
```

## Types
STencil is dynamically typed. The core types:

| Type | Example | Notes |
|------|---------|-------|
| int | `42` | whole numbers |
| float | `3.14` | decimals |
| string | `"hello"` | text (single or double quotes) |
| bool | `true` / `false` | |
| null | `null` | "no value" |
| list | `[1, 2, 3]` | see lesson 6 |
| dict | `{ "k": 1 }` | see lesson 6 |
| object | `User!(...)`, `Account(...)` | see lessons 7 & 8 |

Check a type with `type(x)`:
```stencil
print(type(42));      // int
print(type(3.14));    // float
print(type("hi"));    // string
print(type(true));    // bool
print(type([1,2]));   // list
```

## Optional type annotations
You may annotate a variable's type; it is currently informational (not enforced):
```stencil
let count: int = 5;
let pi: float = 3.14159;
```

## Numbers: int vs float
```stencil
print(7 / 2);     // 3    integer division (both ints)
print(7.0 / 2);   // 3.5  float division (one side is float)
print(3 + 1.5);   // 4.5  mixing promotes to float
```
Whole-number floats print with a trailing `.0`:
```stencil
print(4.0);   // 4.0
print(4);     // 4
```

## Number literals
```stencil
let dec = 255;        // decimal
let hex = 0xFF;       // hexadecimal -> 255 (handy for colors: 0x101828)
let f = 3.14;         // float
print(dec == hex);    // true
```

## Converting between types
```stencil
print(int("42") + 1);     // 43
print(float("3.14"));     // 3.14
print(str(100) + "%");    // 100%
print(bool(0), bool(1));  // false true
```

Next: [Operators & Strings](03_operators_and_strings.md)