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Primitive types

Helios has 5 primitive types:

  • Int (unbounded integer)
  • Real (fixed point real number)
  • Bool (true or false)
  • String (utf-8 text)
  • ByteArray (array of uint8 numbers)

Int​

Helios' Int type represents an unbounded integer (like Haskell's Integer type).

Helios supports common integer literals:

my_decimal = 17
my_binary  = 0b10001
my_hex     = 0x11
my_octal   = 0o121

Large literal integers can be delimited with underscores at power-of-3 positions:

my_large_decimal = 1_000_000

More information about the Int type can be found here.

Real​

Helios' Real type represents a fixed point real number with 6 decimal places, which provides reasonable precision for calculations involving relative fees.

fee = 0.0001 // 0.01%

Similar to Int, underscores can be used at power-of-3 positions to improve readability:

fee = 0.000_1 // 0.01%

More information about the Real type can be found here.

Bool​

The Bool type has two possible literal values: true or false.

Booleans are used throughout validator scripts, and the return type of a validator script can be a boolean. The simplest validator script body is just a literal boolean:

func main(_, _) -> Bool {
    true
}

The equality (==) and inequality (!=) operators, returning boolean results, are defined on all builtin and user types:

func main(datum: Int, redeemer: Int) -> Bool {
    datum == redeemer
}

More information about the Bool type can be found here.

String​

A literal Helios string uses double quotes ("..."):

my_message = "Hello world"

Similar to all other values in Helios, strings are immutable and have a fixed length.

Strings cannot grow after definition. Concatenating two strings creates a new string:

string_1 = "Hello"
string_2 = " world"

result = string_1 + string_2

More information about the String type can be found here.

ByteArray​

The ByteArray type, obviously, represents an array of bytes. A literal ByteArray is either a hexadecimal sequence prefixed by #, or a UTF-8 string prefixed by b:

my_bytes = #48656c6c6f20776f726c64
my_bytes = b"Hello world"

All builtin and user types can be converted into a ByteArray using the builtin serialize method:

cbor_bytes = 123.serialize() // cbor encoding of 123

More information about the ByteArray type can be found here.

Note: a ByteArray can be empty, so the following is valid syntax: my_bytes = #