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Take Away

  • LIGO is a programming language for writing Tezos smart contracts.

  • LIGO compiles scripts written in a high-level language into Michelson script.

  • A smart contract is some code written in Michelson language (a low-level stack-based Turing-complete language).

    • It defines all the entrypoints (invokable functions) of the smart contract.
    • It defines the prototype of each entry point (e.g. specifies the parameters types of the entry point).
    • It defines the storage of the smart contract.
  • The storage is an allocated memory space associated with a smart contract. The description of the storage is done by strongly typing the data structure.

  • Entrypoints of a smart contract describe how to mutate the storage. Executing an entry point takes some of the parameters and a state of the storage and returns a new state of storage and some operations.

Smart contract inputs: entrypoint, parameter and storage. Smart contract outputs: operations and modified storage

FIGURE 1 Smart Contract
  • LIGO functions are the basic building block of smart contracts. Each entrypoint of a contract is a function and each smart contract must have at least one main function that dispatches the control flow to other functions.

  • The option type is used to express if there is a value, of some type, or none. This is especially useful when calling a partial function, that is, a function that is not defined for specific inputs.

  • The keyword failwith(<string_message>) throws an exception and stop the execution of the smart contract.

  • You can transfer tez to an account, or to the function of another smart contract, with Tezos.transaction(<parameter>, <mutez>, <contract>)

To go further

  • You can go to the Tezos Academy which is a fun interactive tutorial on the LIGO language.

  • You can go to Ligolang and try your hand at their IDE online.

  • You can check the smart contract example FundAdvisor with explanatory videos.