Class: Panda::Expression

Inherits:
Node
  • Object
show all
Defined in:
lib/panda/expressions.rb

Overview

The base class for binary Panda expression nodes.

Expression objects have an operator (as a symbol) and left & right operands. Expression classes define a hash of possible operators where the key is the operator and the value is a ‘wordy’ alias for the operator which can be nil.

There is currently no unary expression class because I have not yet figured out a way to implement one in a way that would be useful with this library (for now you’ll just have to apply a bit of Demorgan to get around the absence of a unary negation operator).

Direct Known Subclasses

Boolean, Comparison

Constant Summary collapse

@@inspector = 
Expressers::Inspector

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Node

define_operator_builders_for

Constructor Details

#initialize(left, operator, right) ⇒ Expression

Accepts a left operand, an operator as a symbol, and a right operand. If operator is not one of the possible operators of the invoking Epression class then a Panda::SyntaxError exception is raised.



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# File 'lib/panda/expressions.rb', line 51

def initialize(left, operator, right)
  unless has_operator? operator
    raise SyntaxError, "bad operator :#{operator} for #{self.class}"
  end
  @left, @operator, @right = left, operator, right
end

Instance Attribute Details

#left ⇒ Object (readonly)

Returns the value of attribute left.



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# File 'lib/panda/expressions.rb', line 45

def left
  @left
end

#operator ⇒ Object (readonly)

Returns the value of attribute operator.



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# File 'lib/panda/expressions.rb', line 45

def operator
  @operator
end

#right ⇒ Object (readonly)

Returns the value of attribute right.



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# File 'lib/panda/expressions.rb', line 45

def right
  @right
end

Class Method Details

.has_operator?(op) ⇒ Boolean

Returns true if the class uses the given operator.

Returns:



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# File 'lib/panda/expressions.rb', line 68

def self.has_operator?(op)
  @operators.has_key? op
end

.inspector=(inspector) ⇒ Object

Sets the default expresser class for all Panda AST node’s inspect method. If nil is passed then ruby’s default inspect method is used instead.



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# File 'lib/panda/expressions.rb', line 82

def self.inspector=(inspector)
  @@inspector = inspector
end

.operator_alias_for(op) ⇒ Object

Returns the wordy alias of the operator or nil if it does not have one or if the receiver class does not use the given operator.



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# File 'lib/panda/expressions.rb', line 75

def self.operator_alias_for(op)
  @operators[op.to_sym]
end

.operators ⇒ Object

Returns the receiver class’s hash of possible operators where the key is the operator and the value is the ‘wordy’ alias name of the operator, or nil.



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# File 'lib/panda/expressions.rb', line 62

def self.operators
  @operators
end

Instance Method Details

#has_operator?(op) ⇒ Boolean

Returns true if the receiver’s class uses the given operator.

Returns:



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# File 'lib/panda/expressions.rb', line 88

def has_operator?(op)
  self.class.has_operator? op
end

#inspect ⇒ Object

Overwrites inspect to use the express class method of the expresser class assigned to @@inspector if one exists.

The default expresser is Panda::Expressers::Inspector.



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# File 'lib/panda/expressions.rb', line 104

def inspect
  @@inspector && @@inspector.express(self) || super
end

#operator_alias ⇒ Object

Returns the wordy alias name of the receiver’s operator or nil if it does not have one.



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# File 'lib/panda/expressions.rb', line 95

def operator_alias
  self.class.operator_alias_for @operator
end