Monty.Config.Expression (ExTbpMonty.Core v0.1.0)

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Evaluates the tiny arithmetic dialect Monty's configs use.

Monty has an OmegaConf resolver, np.list_eval, that runs Python's eval over each item of a list, and its configs rely on it for things like ${np.list_eval:[np.pi / 8, np.pi * 2, np.pi * 2]}. Running Python is not an option, so this module parses exactly the language those entries use:

  • number literals (8, 0.7, 1e-3)
  • np.pi
  • +, -, *, / with the usual precedence, and parentheses
  • a list of expressions in brackets

Anything outside that grammar is an error, which is the point: an evaluator that quietly accepts more would be an evaluator we cannot reason about.

Summary

Types

value()

Functions

evaluate(source)

Evaluates a bare expression.

Types

value()

@type value() :: number() | [value()]

Functions

evaluate(source)

@spec evaluate(String.t()) :: {:ok, value()} | {:error, term()}

Evaluates a bare expression.

iex> Monty.Config.Expression.evaluate("np.pi / 8")
0.39269908169872414

iex> Monty.Config.Expression.evaluate("[1, 2 * 3]")
[1.0, 6.0]