Metastatic.Adapters.Erlang (Metastatic v0.10.4)

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Erlang language adapter for MetaAST transformations.

Bridges between Erlang AST (M1) and MetaAST (M2), enabling cross-language code analysis and transformation for Erlang source code.

Erlang AST Structure (M1)

Erlang represents AST as tuples with specific structures. The format varies by construct but generally follows patterns like:

{Type, Line, Value}
{Type, Line, Left, Right}

Examples

# Integer literal
{:integer, 1, 42}

# Variable
{:var, 1, :X}

# Binary operation (addition)
{:op, 1, :+, {:var, 1, :X}, {:integer, 1, 5}}

# Function call
{:call, 1, {:atom, 1, :foo}, [{:integer, 1, 1}, {:integer, 1, 2}]}

# Case expression
{:case, 1, {:var, 1, :X},
 [{:clause, 1, [{:integer, 1, 1}], [], [{:atom, 1, :ok}]}]}

M1 ↔ M2 Transformations

This adapter performs bidirectional transformations between Erlang AST (M1) and MetaAST (M2):

Literals

# M1 → M2
{:integer, _, 42}           → {:literal, :integer, 42}
{:float, _, 3.14}           → {:literal, :float, 3.14}
{:string, _, 'hello'}       → {:literal, :string, "hello"}
{:atom, _, true}            → {:literal, :boolean, true}
{:atom, _, undefined}       → {:literal, :null, nil}

Variables

{:var, _, :X}               → {:variable, "X"}

Binary Operations

{:op, _, :+, left, right}   → {:binary_op, :arithmetic, :+, left, right}
{:op, _, :==, left, right}  → {:binary_op, :comparison, :==, left, right}

Function Calls

{:call, _, func, args}      → {:function_call, "func", args}

Round-Trip Fidelity

The adapter achieves >90% round-trip fidelity for M2.1 (Core) constructs. Metadata preserves:

  • Line numbers
  • Variable names (case-sensitive)
  • Erlang-specific type information

Usage

# Parse Erlang source
{:ok, ast} = Metastatic.Adapters.Erlang.parse("X + 5.")

# Transform to MetaAST
{:ok, meta_ast, metadata} = Metastatic.Adapters.Erlang.to_meta(ast)

# Transform back to Erlang AST
{:ok, ast2} = Metastatic.Adapters.Erlang.from_meta(meta_ast, metadata)

# Unparse to source
{:ok, source} = Metastatic.Adapters.Erlang.unparse(ast2)

Theory

This adapter implements the Galois connection:

α_Erlang: AS_Erlang → MetaAST × Metadata
ρ_Erlang: MetaAST × Metadata → AS_Erlang

Where:

  • α_Erlang is to_meta/1 (abstraction)
  • ρ_Erlang is from_meta/2 (reification)