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55 lines
1.1 KiB
55 lines
1.1 KiB
require_relative "error"
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module Lox
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class Environment
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attr_reader :values, :enclosing
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def initialize(enclosing = nil)
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@enclosing = enclosing
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@values = {}
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end
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def define(name, value)
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@values[name] = value
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end
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def ancestor(distance)
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env = self
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distance.times { env = env.enclosing }
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env
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end
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def get(token)
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name = token.lexeme
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if @values.has_key?(name)
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@values[name]
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elsif @enclosing
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@enclosing.get(token)
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else
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raise RuntimeError.new(token, "Undefined variable '#{name}'.")
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end
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end
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def get_at(distance, name)
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ancestor(distance).values.fetch(name)
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end
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def assign(name, value)
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lexeme = name.lexeme
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if @values.has_key?(lexeme)
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@values[lexeme] = value
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elsif @enclosing
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@enclosing.assign(name, value)
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else
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raise RuntimeError.new(name, "Undefined variable '#{lexeme}'.")
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end
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end
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def assign_at(distance, name, value)
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ancestor(distance).values[name.lexeme] = value
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end
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end
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end
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