The Edge Specification

All Edge, No Drag.

This document defines Edge, a domain specific language for the Ethereum Virtual Machine (EVM).

Edge is a high level, strongly statically typed, multi-paradigm language. It provides:

  • A thin layer of abstraction over the EVM's instruction set architecture (ISA).
  • An extensible polymorphic type system with subtyping.
  • First class support for modules and code reuse.
  • Compile time code execution to fine-tune the compiler's input.

Edge's syntax is similar to Rust and Zig where intuitive, however, the language is not designed to be a general purpose language with EVM features as an afterthought. Rather, it is designed to extend the EVM instruction set with a reasonable type system and syntax sugar over universally understood programming constructs.

Notation

This specification uses a grammar similar to Extended Backus-Naur Form (EBNF) with the following rules.

  • Non-terminal tokens are wrapped in angle brackets <ident>.
  • Terminal tokens are wrapped in double quotes "const".
  • Optional items are wrapped in brackets ["mut"].
  • Sequences of zero or more items are wrapped in parenthesis and suffixed with a star ("," <ident>)*.
  • Sequences of one or more items are wrapped in parenthesis and suffixed with a plus (<ident>)+.

In contrast to EBNF, we define a rule that all items are non-atomic, that is to say arbitrary whitespace characters \n, \t, and \r may surround all tokens unless wrapped with curly braces { "0x" (<hex_digit>)* }.

Generally, we use long-formed names for clarity of each token, however, common tokens are abbreviated and defined as follows:

Disambiguation

This section contains context that be required throughout the specification.

Return vs Return™️

The word "return" refers to two different behaviors, returned values from expressions and the halting return opcode.

When "return" is used, this refers to the values returned from expressions, that is to say the values left on the stack, if any.

When "halting return" is used, this refers to the EVM opcode return that halts execution and returns a value from a slice of memory to the caller of the current execution context.