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Move Language

language/README.md

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Move is a new programming language developed to provide a safe and programmable foundation for the Diem Blockchain.

Overview

The Move language directory consists of four main parts:

  • virtual machine (VM) — contains the bytecode format, a bytecode interpreter, and infrastructure for executing a block of transactions. This directory also contains the infrastructure to generate the genesis block.

  • bytecode verifier — contains a static analysis tool for rejecting invalid Move bytecode. The virtual machine runs the bytecode verifier on any new Move code it encounters before executing it. The compiler runs the bytecode verifier on its output and surfaces the errors to the programmer.

  • move-lang — contains the Move source language compiler.

  • standard library — contains the Move code for the core system modules (such as DiemAccount), as well as the standard library transaction scripts.

How the Move Language Fits Into Diem Core

Diem Core components interact with the language component through the VM. Specifically, the admission control component uses a limited, read-only subset of the VM functionality to discard invalid transactions before they are admitted to the mempool and consensus. The execution component uses the VM to execute a block of transactions.

Exploring the Move language

  • You can find many small Move examples in the tests directory. The easiest way to experiment with Move is to create a new test in this directory and run it with cargo test.
  • More substantial examples can be found in the standard library directory. The Two particularly notable ones are DiemAccount, which implements accounts on the Diem blockchain, and Diem, which implements generic currency logic used by all of the currencies the Diem payment network supports.
  • The transaction scripts supported in the Diem blockchain are also in the standard library directory. Move tests and local instances of the Diem blockchain can execute arbitrary transaction scripts, but the Diem blockchain and testnet are limited to accepting the scripts in this directory.