Class: Scope

Inherits:
Object
  • Object
show all
Defined in:
lib/nodes.rb

Overview

Class to handle scopes when evaluating AST.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(parent_scope = nil) ⇒ Scope

Returns a new instance of Scope.



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# File 'lib/nodes.rb', line 8

def initialize(parent_scope = nil)
  @identifiers = {}
  @non_local_variables = []
  @parent_scope = parent_scope
end

Instance Attribute Details

#identifiers ⇒ Object (readonly)

Returns the value of attribute identifiers.



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# File 'lib/nodes.rb', line 7

def identifiers
  @identifiers
end

#non_local_variables ⇒ Object (readonly)

Returns the value of attribute non_local_variables.



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# File 'lib/nodes.rb', line 7

def non_local_variables
  @non_local_variables
end

#parent_scope ⇒ Object (readonly)

Returns the value of attribute parent_scope.



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# File 'lib/nodes.rb', line 7

def parent_scope
  @parent_scope
end

Instance Method Details

#get_identifier(name) ⇒ Object

Get value of identifier in current or parent scope(s) if defined.



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# File 'lib/nodes.rb', line 51

def get_identifier(name)
  scope = get_scope(name)
  if scope
    return scope.identifiers[name]
  else
    raise NameError,"Identifier #{name} not defined in scope."
  end
end

#get_scope(name) ⇒ Object

Get first scope where identifier is defined.



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# File 'lib/nodes.rb', line 61

def get_scope(name)
  if @identifiers.has_key?(name)
    return self
  elsif @parent_scope
    return @parent_scope.get_scope(name)
  end
end

#is_function?(name) ⇒ Boolean

Checks if a identifier is a function.

Returns:

  • (Boolean) 


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# File 'lib/nodes.rb', line 70

def is_function?(name)
  scope = get_scope(name)
  return false unless scope

  id_value = scope.get_identifier(name)
  return id_value.is_a?(Hash) 
end

#set_function(name, block, parameters) ⇒ Object

Set a function in current scope.



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# File 'lib/nodes.rb', line 79

def set_function(name, block, parameters)
  @identifiers[name] = {:parameters => parameters, :block => block}
end

#set_non_local_variable(name) ⇒ Object

Add non local variable used in scope



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# File 'lib/nodes.rb', line 44

def set_non_local_variable(name)
  unless @non_local_variables.include?(name) || is_function?(name)
    @non_local_variables.append(name)
  end
end

#set_variable(name, op, expression) ⇒ Object

Set variable in current scope



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# File 'lib/nodes.rb', line 15

def set_variable(name, op, expression)

  # Checks if the variable has been used as a non-local variable, if true: raise NameError
  if @non_local_variables.include?(name)
    raise NameError, "Local identifier #{name} referenced before assignment"
  end

  if op == '='
    @identifiers[name] = expression
  else

    # Checks if the variable is local, raise NameError if otherwise
    unless @identifiers.has_key?(name)
      raise NameError, "Local identifier #{name} referenced before assignment"
    end

    if op == '+='
      @identifiers[name] += expression
    else
      if @identifiers[name].is_a?(String) || expression.is_a?(String)
        raise TypeError, "Operation #{op} is not allowed for identifier #{name} or the expression as they must not be strings"
      else
        @identifiers[name] -= expression
      end
    end
  end
end