Elle is a compiler focused on generating code for the Ethereum Virutal Machine (EVM). What sets is apart from other Ethereum compiler technologies is that it is foundationally verified: that is, it is implemented inside of Isabelle, a proof assistant that enables programmers to state and prove mathematical theorems about their code. In the case of Elle, a theorem exists stating that the behavior of the code output by the Elle compiler matches the behavior of its input (see Correctness).

Assuming we trust the model of Elle’s source language (an LLL/Yul/WASM-like structured programming layer on top of EVM) and the semantics of EVM (drawn from the Eth-Isabelle project, we can have complete confidence that Elle generates EVM programs that match the programmer’s intent: that is, that behave the same way that input programs are supposed to behave.

In the rest of this documentation, we’ll cover :ref:how to install Elle <installation>, how to use Elle’s FourL frontend <usage_> as an end user to compile smart contracts written in the LLL language into EVM bytecode. Next, we’ll dive into the details of Elle’s source-level representation, covering its syntax <syntax_> and its formal semantics <semantics_>. Next, we’ll talk about the internals of the implementation <implementation_> of the Elle compiler (along with the FourL frontend) as well as its correctness proof <correctness_>.

Elle is intended to be supplanted by Gazelle, a . As such, Elle itself is unlikely to see significant changes at this point. Nonetheless, Elle as it exists is a useful system: it can be used to compile real-world LLL smart contracts; namely Dan Ellison’s Echo smart contract, Ben Edgington’s LLL-ERC20 token contract, and the LLL implementation of the ENS registry. For these examples, see the tests directory.