Built-in variables

A built-in variable is a variable of the Standard library.

Name	Description
Buy	Order type
CEILING DOWN FLOOR HALFEVEN HALFUP	Rounding methods used in the math functions fraction, log, pow
height	Blockchain height at the moment of the script execution
lastBlock	BlockInfo structure containing headers of the current block at the moment of the script execution
nil	Variable that contains an empty list. The variable is used for creating lists. For example, instead of: let a = [5,6] you can write: let b = 5::6::nil Lists are created using both methods. The first method is a syntactic sugar
NOALG MD5 SHA1 SHA224 SHA256 SHA384 SHA512 SHA3224 SHA3256 SHA3384 SHA3512	Variables that are passed as the first parameter to the rsaVerify function
Sell	Order type
this	• For a dApp script or an account script: the Address structure • For an asset script: the Asset structure
tx	Transaction or order
unit	Variable that contains an object of Unit type. Example 1 the deposit function transfers 5 WAVELETs to the account, that called this function. {-# STDLIB_VERSION 8 #-} {-# CONTENT_TYPE DAPP #-} {-# SCRIPT_TYPE ACCOUNT #-} @Callable(inv) func deposit() = { ( [ # Transfer 5 WAVELETs to the inv.caller account # WAVES does not have a token ID, unit is specified instead ScriptTransfer(inv.caller, 5, unit) ], unit ) } Example 2 The assetInfo function requests information about the token by its ID. Next, the isDefined function checks that a token with this ID exists on the blockchain. let asset = assetInfo(base58'8LQW8f7P5d5PZM7GtZEBgaqRPGSzS3DfPuiXrURJ4AJS') asset.isDefined() Instead of calling the isDefined function, you may use the equality with unit. asset != unit # Expression asset != unit is equivalent to the expression token.isDefined()