Function purity analysis at the MetaAST level.

Analyzes code to determine if it's pure (no side effects) or impure (has side effects like I/O, mutations, random operations, etc.).

Works across all supported languages by operating on the unified MetaAST representation.

Purity Definition

A pure function:

• Always returns the same output for the same input (deterministic)
• Has no side effects (no I/O, no mutations, no global state access)
• Doesn't depend on external state

An impure function has one or more of:

• I/O operations (print, file access, network, database)
• Mutations (modifying variables, especially in loops)
• Non-deterministic operations (random, time/date)
• Exception handling (raising/catching exceptions)

Usage

alias Metastatic.{Document, Analysis.Purity}

# Analyze a document
ast = {:binary_op, :arithmetic, :+, {:variable, "x"}, {:literal, :integer, 5}}
doc = Document.new(ast, :elixir)
{:ok, result} = Purity.analyze(doc)

result.pure?              # => true
result.effects            # => []
result.confidence         # => :high
result.summary            # => "Function is pure"

Examples

# Pure arithmetic
iex> ast = {:binary_op, [category: :arithmetic, operator: :+], [{:literal, [subtype: :integer], 1}, {:literal, [subtype: :integer], 2}]}
iex> doc = Metastatic.Document.new(ast, :python)
iex> {:ok, result} = Metastatic.Analysis.Purity.analyze(doc)
iex> result.pure?
true

# Impure I/O
iex> ast = {:function_call, [name: "print"], [{:literal, [subtype: :string], "hello"}]}
iex> doc = Metastatic.Document.new(ast, :python)
iex> {:ok, result} = Metastatic.Analysis.Purity.analyze(doc)
iex> result.pure?
false
iex> result.effects
[:io]