Types

NexScript is a statically typed language, which means that the type of each variable needs to be specified. Types can also be implicitly or explicitly cast to other types. For a quick reference of the various casting possibilities, see Type Casting.

Boolean

bool: The possible values are constants true and false.

Operators:

• ! (logical negation)
• && (logical conjunction, “and”)
• || (logical disjunction, “or”)
• == (equality)
• != (inequality)

note

The operators || and && don't apply common short-circuiting rules. This means that in the expression f(x) || g(y), g(y) will still be executed even if f(x) evaluates to true.

Integer

int: Signed integer of 64 bit size.

Operators:

• Comparisons: <=, <, ==, !=, >=, > (all evaluate to bool)
• Arithmetic operators: +, -, unary -, *, /, % (modulo).

Note the clear lack of the ** (exponentiation) operator as well as any bitwise operators.

caution

The script will fail when the right hand side of Division and modulo operations is zero.

Date Parsing

Dates and times are always represented as integers. To get the UTC timestamp of a date use the built-in parser to avoid any potential errors. This will take a date in the format date("YYYY-MM-DDThh:mm:ss") and convert it to an integer timestamp.

Example

int timestamp = date("2021-02-17T01:30:00");
require(timestamp == 1613554200);

String

string: UTF8-encoded byte sequence.

Operators:

• + (concatenation)
• == (equality)
• != (inequality)

Members:

• length: Number of characters in the string.
• split(int): Splits the string at the specified index and returns a tuple with the two resulting strings.
• reverse(): Reverses the string.

caution

The script will fail if split() is called with an index that is out of bounds.

Bytes

bytes: Byte sequence. Can optionally be bound to a byte length by specifying e.g. bytes4, bytes32, bytes64. It is also possible to use byte as an alias for bytes1.

Operators:

• + (concatenation)
• == (equality)
• != (inequality)

Members:

• length: Number of bytes in the sequence.
• split(int): Splits the byte sequence at the specified index and returns a tuple with the two resulting byte sequences.
• reverse(): Reverses the byte sequence.

caution

The script will fail if split() is called with an index that is out of bounds.

Bytes types with semantic meaning

Some byte sequences hold specific meanings inside Nexa contracts. These have been granted their own types separate from the regular bytes type.

Public Key

pubkey: Byte sequence representing a public key. Generally 33 bytes long.

Operators:

• == (equality)
• != (inequality)

Transaction Signature

sig: Byte sequence representing a transaction signature. Generally 65 bytes long.

Operators:

• == (equality)
• != (inequality)

Data Signature

datasig: Byte sequence representing a data signature. Generally 64 bytes long.

Operators:

• == (equality)
• != (inequality)

Array

Arrays are not assignable and can only be used with the checkMultisig function using the following syntax:

checkMultisig([sig1, sig2], [pk1, pk2, pk3]);

Tuple

Tuples are the type that is returned when calling the split member function on a string or bytes type. Their first or second element can be accessed through an indexing syntax similar to other languages:

string question = "What is Nexa's ticker?";
string answer = question.split(12)[0].split(8)[1];

It is also possible to assign both sides of the tuple at once with a destructuring syntax:

string trilemma, string solved = "100,000TPS".split(7);
require(trilemma == solved);

Type Casting

Type casting can be done both explicitly and implicitly as illustrated below. pubkey, sig and datasig can be implicitly cast to bytes, meaning they can be used anywhere where you would normally use a bytes type. Explicit type casting can be done with a broader range of types, but is still limited. The syntax of this explicit type casting is illustrated below. Note that you can also cast to bounded bytes types.

note

When casting integer types to bytes of a certain size, the integer value is padded with zeros. e.g. bytes4(0) == 0x00000000. It is also possible to pad with a variable number of zeros, by passing in a size parameter, which indicates the size of the output. e.g. bytes(0, 4 - 2) == 0x0000. Lastly, note that bytes(0) == 0x.

caution

When casting bytes types to integer, you should be sure that the bytes value fits inside a 64-bit signed integer, or the script will fail.

See the following table for information on which types can be cast to other which other types.

Type	Implicitly castable to	Explicitly castable to
int		bytes, bool
bool		int
string		bytes
bytes		sig, pubkey, int
pubkey	bytes	bytes
sig	bytes	bytes
datasig	bytes	bytes

Example

pubkey pk = pubkey(0x0000);
bytes editedPk = bytes(pk) + 0x1234;
bytes4 integer = bytes4(25);