Data Types

Praia has 7 types:

Type	Examples	Notes
nil	nil	The absence of a value
bool	true, false
int	42, 0xFF, 0b1010, 0o17	64-bit integer (exact up to 2^63). Supports hex, binary, octal.
float	3.14, 1e3, 2.5e-4	Double-precision float. Supports scientific notation.
string	"hello"	UTF-8, supports interpolation, escape sequences, and Unicode (\u{...})
array	[1, 2, 3]	Ordered, mixed-type, reference semantics
map	{name: "Ada"}	Key-value pairs, reference semantics
function	func add(a, b) { ... }	First-class, supports closures

Use type() to check a value’s type at runtime:

print(type(42))         // int
print(type(3.14))       // float
print(type("hi"))       // string
print(type([1, 2]))     // array
print(type({a: 1}))     // map

Number literals

Integers

Integers support multiple bases and underscores as visual separators:

42                // decimal
0xFF              // hex
0b1010            // binary
0o755             // octal
1_000_000         // underscores ignored (readability)
0xFF_FF           // works in any base

Floats

Floats support decimal points and scientific notation:

3.14              // decimal float
1e3               // 1000.0 (scientific notation)
2.5e-4            // 0.00025
1_000.5           // separators in floats too

Integer overflow automatically promotes to float rather than wrapping.

Arithmetic rules

• int + int, int - int, int * int, int % int produce int
• Anything involving a float produces float
• / always returns float: 7 / 2 gives 3.5

42 + 8          // 50 (int)
42 + 0.5        // 42.5 (float)
7 / 2           // 3.5 (always float)
7 % 2           // 1 (int)

Integers are 64-bit, so they are exact up to 2^63:

let big = 9007199254740993
print(big + 1)     // 9007199254740994 (exact)

Ints and floats compare by value: 42 == 42.0 is true.

Truthiness

Only nil and false are falsy. Everything else — including 0, "" (empty string), and [] (empty array) — is truthy.

if (0)       { print("truthy") }   // prints (0 is truthy)
if ("")      { print("truthy") }   // prints (empty string is truthy)
if ([])      { print("truthy") }   // prints (empty array is truthy)
if (nil)     { print("truthy") }   // does not print
if (false)   { print("truthy") }   // does not print

To check for empty strings or arrays, use len():

if (len(name) > 0) { print("has name") }
if (len(items) > 0) { print("has items") }

Type checking with is

The is operator checks types and class hierarchy:

42 is "int"             // true
"hello" is "string"     // true
[1, 2] is "array"       // true

class Animal {}
class Dog extends Animal {}
let d = Dog()
d is Dog                // true
d is Animal             // true (walks inheritance chain)

Supported type strings: "nil", "bool", "int", "float", "string", "array", "map", "function", "instance".