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Intermediate Representation (IR)

This crate contains the intermediate representation for AirScript, AirIR.

The purpose of the AirIR is to provide a simple and accurate representation of an AIR that allows for optimization and translation to constraint evaluator code in a variety of target languages.

Generating the AirIR

Generate an AirIR from an AirScript AST (the output of the AirScript parser) using the new method. The new method will return a new AirIR or an Error of type SemanticError if it encounters any errors while processing the AST.

The new method will first iterate through the source sections that contain declarations to build a symbol table with constants, trace columns, public inputs, periodic columns and random values. It will return a SemanticError if it encounters a duplicate, incorrect, or missing declaration. Once the symbol table is built, the constraints and intermediate variables in the boundary_constraints and integrity_constraints sections of the AST are processed. Finally, new returns a Result containing the AirIR or a SemanticError.

Example usage:

// parse the source string to a Result containing the AST or an Error
let ast = parse(source.as_str()).expect("Parsing failed");

// process the AST to get a Result containing the AirIR or an Error
let ir = AirIR::new(&ast)

AirIR

Although generation of an AirIR uses a symbol table while processing the source AST, the internal representation only consists of the following:

  • Name of the AIR definition represented by the AirIR.
  • Segment Widths, represented by a vector that contains the width of each trace segment (currently main and auxiliary).
  • Constants, represented by a vector that maps an identifier to a constant value.
  • Public inputs, represented by a vector that maps an identifier to a size for each public input that was declared. (Currently, public inputs can only be declared as fixed-size arrays.)
  • Periodic columns, represented by an ordered vector that contains each periodic column's repeating pattern (as a vector).
  • Constraints, represented by the combination of:
    • a directed acyclic graph (DAG) without duplicate nodes.
    • a vector of ConstraintRoot for each trace segment (e.g. main or auxiliary), where ConstraintRoot contains the node index in the graph where each of the constraint starts and the constraint domain which specifies the row(s) accessed by each of the constraints.
    • contains both boundary and integrity constraints.