Class: Einstein::Evaluator

Inherits:
Processor show all
Defined in:
lib/einstein/evaluator.rb

Overview

This processor walks the AST and evaluates the values of the nodes.

Instance Method Summary collapse

Methods inherited from Processor

#process

Constructor Details

#initialize(scope = {}) ⇒ Evaluator

Initialize a new instance of this processor with the given scope, as a hash. This scope should provide a mapping of variable names to values.



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# File 'lib/einstein/evaluator.rb', line 9

def initialize(scope = {})
  # Convert symbol keys into strings.
  @scope = scope.inject({}) do |hash, (key, value)|
    hash[key.to_s] = value
    hash
  end
end

Instance Method Details

#process_add(exp) ⇒ Object

Adds the left and right values of exp.



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# File 'lib/einstein/evaluator.rb', line 59

def process_add(exp)
  process(exp[1]) + process(exp[2])
end

#process_bitwise_and(exp) ⇒ Object

Performs a bitwise AND with the left and right values of exp.



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# File 'lib/einstein/evaluator.rb', line 81

def process_bitwise_and(exp)
  process(exp[1]) & process(exp[2])
end

#process_bitwise_not(exp) ⇒ Object

Performs a bitwise NOT operation on the value of exp.



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# File 'lib/einstein/evaluator.rb', line 33

def process_bitwise_not(exp)
  ~process(exp[1])
end

#process_bitwise_or(exp) ⇒ Object

Performs a bitwise OR with the left and right values of exp.



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# File 'lib/einstein/evaluator.rb', line 91

def process_bitwise_or(exp)
  process(exp[1]) | process(exp[2])
end

#process_bitwise_xor(exp) ⇒ Object

Performs a bitwise XOR with the left and right values of exp.



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# File 'lib/einstein/evaluator.rb', line 86

def process_bitwise_xor(exp)
  process(exp[1]) ^ process(exp[2])
end

#process_divide(exp) ⇒ Object

Divides the left value of exp by the right value of exp. Will raise ZeroDivisionError if the right value of exp evaluates to 0.



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# File 'lib/einstein/evaluator.rb', line 49

def process_divide(exp)
  process(exp[1]) / process(exp[2])
end

#process_exponent(exp) ⇒ Object

Raises the left value of exp by the right value of exp.



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# File 'lib/einstein/evaluator.rb', line 38

def process_exponent(exp)
  process(exp[1]) ** process(exp[2])
end

#process_lit(exp) ⇒ Object

Returns the value of exp.



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# File 'lib/einstein/evaluator.rb', line 18

def process_lit(exp)
  exp[1]
end

#process_lshift(exp) ⇒ Object

Performs a bitwise left shift of the left value of exp by the number of bits specified in the right value of exp.



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# File 'lib/einstein/evaluator.rb', line 70

def process_lshift(exp)
  process(exp[1]) << process(exp[2])
end

#process_modulus(exp) ⇒ Object

Performs a modulus operation for the left and right values of exp.



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# File 'lib/einstein/evaluator.rb', line 54

def process_modulus(exp)
  process(exp[1]) % process(exp[2])
end

#process_multiply(exp) ⇒ Object

Multiplies the left and right values of exp.



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# File 'lib/einstein/evaluator.rb', line 43

def process_multiply(exp)
  process(exp[1]) * process(exp[2])
end

#process_resolve(exp) ⇒ Object

Performs a lookup for the value of exp inside this processor’s scope. Raises ResolveError if the variable is not in scope.

Raises:



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# File 'lib/einstein/evaluator.rb', line 97

def process_resolve(exp)
  raise ResolveError, "Undefined variable: #{exp[1]}" unless @scope.has_key?(exp[1])
  @scope[exp[1]]
end

#process_rshift(exp) ⇒ Object

Performs a bitwise right shift of the left value of exp by the number of bits specified in the right value of exp.



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# File 'lib/einstein/evaluator.rb', line 76

def process_rshift(exp)
  process(exp[1]) >> process(exp[2])
end

#process_subtract(exp) ⇒ Object

Subtracts the right value of exp by the left value of exp.



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# File 'lib/einstein/evaluator.rb', line 64

def process_subtract(exp)
  process(exp[1]) - process(exp[2])
end

#process_unary_minus(exp) ⇒ Object

Returns the negated value of exp.



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# File 'lib/einstein/evaluator.rb', line 28

def process_unary_minus(exp)
  -process(exp[1])
end

#process_unary_plus(exp) ⇒ Object

Returns the value of exp.



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# File 'lib/einstein/evaluator.rb', line 23

def process_unary_plus(exp)
  process(exp[1])
end