Intrinsic functions

Intrinsic functions are special and usually correspond to dedicated Zinc VM instructions.


Prints its arguments to the terminal. Only for debugging purposes.


  • format string literal (str)
  • rest of the arguments to print

Return type: ()

Note: This function is special, as it accepts an arbitrary number of arguments of any type after the format string.


Checks if the boolean expression is true. If it is not, the circuit fails with an error passed as the second argument.


  • boolean expression (bool)
  • error message string literal (str)

Return type: ()

This is the only function able to halt the application execution.

<Contract>::transfer function

Executes a transfer which is eventually sent to the zkSync platform.

Is automatically defined as a method in every smart contract.


  • sender: <Contract>
  • recipient: u160
  • token_address: u160
  • amount: u248

Returns: ()

<Contract>::fetch function

Loads a contract instance from the Zandbox server.

Is automatically defined as a static function in every smart contract.


  • address: u160

Returns: <Contract>