Module: Pikuri::Tool::Calculator

Defined in:
lib/pikuri/tool/calculator.rb

Overview

Evaluates a basic arithmetic expression with Python operator syntax and semantics, via the hand-rolled recursive-descent Parser below.

Why hand-rolled rather than a gem: the previous backend, dentaku, pulled in concurrent-ruby (~16k lines of Ruby — the single heaviest audit item in pikuri’s whole dependency closure) plus bigdecimal and tsort, all to evaluate four-function arithmetic. The ~100 lines here implement Python’s expression grammar directly, which also retires the old preprocessing step that rewrote Python’s ** into dentaku’s ^ dialect — the model’s native syntax is now simply the grammar.

Scope is intentionally narrow: operators (+, -, *, /, //, %, **), unary minus, parentheses, and integer / decimal / e-notation literals. No variables, functions, or booleans — those would mean teaching the model a dialect, which we specifically want to avoid for this tool.

Defined Under Namespace

Classes: Error, Parser

Class Method Summary collapse

Class Method Details

.calculate(expression) ⇒ String

Evaluate expression and return the result formatted as a String. Parse and arithmetic failures (division by zero, overflow to infinity, complex results) are caught and returned as “Error: …” strings so the model can read the failure as the next observation and self-correct rather than crashing the agent loop.

Parameters:

  • expression (String) —

    Python-syntax arithmetic expression

Returns:

  • (String) —

    numeric result, or “Error: …” on failure



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# File 'lib/pikuri/tool/calculator.rb', line 40

def self.calculate(expression)
  result = Parser.new(expression).parse
  if result.is_a?(Float) && !result.finite?
    raise Error, "result of #{expression.inspect} is not a finite number"
  end

  format_result(result)
rescue Error => e
  "Error: #{e.message}"
end