Class: Porolog::Predicate

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

Overview

A Porolog::Predicate corresponds to a Prolog predicate. It contains rules (Porolog::Rule) and belongs to a Porolog::Scope. When provided with arguments, it produces a Porolog::Arguments.

Author:

  • Luis Esteban

Defined Under Namespace

Classes: NameError, PredicateError

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, scope_name = Predicate.scope.name) ⇒ Predicate

Initializes a Porolog::Predicate and registers it by its name.

Parameters:

  • name (#to_sym) —

    the input object to read from

  • scope_name (defaults to: Predicate.scope.name) —

    the name of the scope in which to register the Predicate; if omitted, defaults to the name of the current scope

Raises:



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# File 'lib/porolog/predicate.rb', line 68

def initialize(name, scope_name = Predicate.scope.name)
  @name  = name.to_sym
  @rules = []
  
  raise NameError.new("Cannot name a predicate 'predicate'") if @name == :predicate
  
  scope = Scope[scope_name] || Scope.new(scope_name)
  scope[@name] = self
end

Instance Attribute Details

#name ⇒ Object (readonly)

Name of the Predicate.



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# File 'lib/porolog/predicate.rb', line 18

class Predicate
  
  # Error class for rescuing or detecting any Predicate error.
  class PredicateError < PorologError   ; end
  # Error class indicating an error with the name of a Predicate.
  class NameError      < PredicateError ; end
  
  attr_reader :name, :rules
  
  # Returns the current scope, or sets the current scope if a paramter is provided
  # (creating the new scope if necessary).
  # @param scope_name [Object] the name (or otherwise object) used to register a scope.
  # @return [Porolog::Scope] the current Scope.
  def self.scope(scope_name = nil)
    if scope_name
      @@current_scope = Scope[scope_name] || Scope.new(scope_name)
    else
      @@current_scope
    end
  end
  
  # Sets the current scope (creating the new scope if necessary.
  # @param scope_name [Object] the name (or otherwise object) used to register a scope.
  # @return [Porolog::Scope] the current Scope.
  def self.scope=(scope_name)
    if scope_name
      @@current_scope = Scope[scope_name] || Scope.new(scope_name)
    end
    @@current_scope
  end
  
  # Resets the current scope to default and deregisters builtin predicates.
  # @return [Porolog::Scope] the current Scope.
  def self.reset
    scope(:default)
    @builtin_predicate_ids = {}
  end
  
  # Looks up a Predicate in the current scope by its name.
  # @param name [Object] the name (or otherwise object) used to register a scope.
  # @return [Porolog::Predicate] the Predicate with the given name.
  def self.[](name)
    @@current_scope[name]
  end
  
  reset
  
  # Initializes a Porolog::Predicate and registers it by its name.
  # @param name [#to_sym] the input object to read from
  # @param scope_name the name of the scope in which to register the Predicate; if omitted, defaults to the name of the current scope
  def initialize(name, scope_name = Predicate.scope.name)
    @name  = name.to_sym
    @rules = []
    
    raise NameError.new("Cannot name a predicate 'predicate'") if @name == :predicate
    
    scope = Scope[scope_name] || Scope.new(scope_name)
    scope[@name] = self
  end
  
  # Creates a new Predicate, or returns an existing Predicate if one already exists with the given name in the current scope.
  # @return [Porolog::Predicate] a new or existing Predicate.
  def self.new(*args)
    name, _ = *args
    scope[name.to_sym] || super
  end
  
  # Create Arguments for the Predicate.
  # Provides the syntax options:
  # * p.(x,y,z)
  # @return [Porolog::Arguments] Arguments of the Predicate with the given arguments.
  def call(*args)
    Arguments.new(self,args)
  end
  
  # Create Arguments for the Predicate.
  def arguments(*args)
    Arguments.new(self,args)
  end
  
  # Add a Rule to the Predicate.
  # @param rule [Object] the name (or otherwise object) used to register a scope.
  # @return [Array<Porolog::Rule>] the Predicate's rule.
  def <<(rule)
    @rules << rule
  end
  
  # A pretty print String of the Predicate.
  # @return [String] the Predicate as a String.
  def inspect
    lines = []
    
    if @rules.size == 1
      lines << "#{@name}:-#{@rules.first.inspect}"
    else
      lines << "#{@name}:-"
      @rules.each do |rule|
        lines << rule.inspect
      end
    end
      
    lines.join("\n")
  end
  
  # Return a builtin Predicate based on its key.
  # @param key [Symbol] the name (or otherwise object) used to register a scope.
  # @return [Porolog::Predicate] a Predicate with the next id based on the key.
  def self.builtin(key)
    @builtin_predicate_ids[key] ||= 0
    @builtin_predicate_ids[key]  += 1
    
    self.new("_#{key}_#{@builtin_predicate_ids[key]}")
  end
  
end

#rules ⇒ Object (readonly)

Rules of the Predicate.



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# File 'lib/porolog/predicate.rb', line 18

class Predicate
  
  # Error class for rescuing or detecting any Predicate error.
  class PredicateError < PorologError   ; end
  # Error class indicating an error with the name of a Predicate.
  class NameError      < PredicateError ; end
  
  attr_reader :name, :rules
  
  # Returns the current scope, or sets the current scope if a paramter is provided
  # (creating the new scope if necessary).
  # @param scope_name [Object] the name (or otherwise object) used to register a scope.
  # @return [Porolog::Scope] the current Scope.
  def self.scope(scope_name = nil)
    if scope_name
      @@current_scope = Scope[scope_name] || Scope.new(scope_name)
    else
      @@current_scope
    end
  end
  
  # Sets the current scope (creating the new scope if necessary.
  # @param scope_name [Object] the name (or otherwise object) used to register a scope.
  # @return [Porolog::Scope] the current Scope.
  def self.scope=(scope_name)
    if scope_name
      @@current_scope = Scope[scope_name] || Scope.new(scope_name)
    end
    @@current_scope
  end
  
  # Resets the current scope to default and deregisters builtin predicates.
  # @return [Porolog::Scope] the current Scope.
  def self.reset
    scope(:default)
    @builtin_predicate_ids = {}
  end
  
  # Looks up a Predicate in the current scope by its name.
  # @param name [Object] the name (or otherwise object) used to register a scope.
  # @return [Porolog::Predicate] the Predicate with the given name.
  def self.[](name)
    @@current_scope[name]
  end
  
  reset
  
  # Initializes a Porolog::Predicate and registers it by its name.
  # @param name [#to_sym] the input object to read from
  # @param scope_name the name of the scope in which to register the Predicate; if omitted, defaults to the name of the current scope
  def initialize(name, scope_name = Predicate.scope.name)
    @name  = name.to_sym
    @rules = []
    
    raise NameError.new("Cannot name a predicate 'predicate'") if @name == :predicate
    
    scope = Scope[scope_name] || Scope.new(scope_name)
    scope[@name] = self
  end
  
  # Creates a new Predicate, or returns an existing Predicate if one already exists with the given name in the current scope.
  # @return [Porolog::Predicate] a new or existing Predicate.
  def self.new(*args)
    name, _ = *args
    scope[name.to_sym] || super
  end
  
  # Create Arguments for the Predicate.
  # Provides the syntax options:
  # * p.(x,y,z)
  # @return [Porolog::Arguments] Arguments of the Predicate with the given arguments.
  def call(*args)
    Arguments.new(self,args)
  end
  
  # Create Arguments for the Predicate.
  def arguments(*args)
    Arguments.new(self,args)
  end
  
  # Add a Rule to the Predicate.
  # @param rule [Object] the name (or otherwise object) used to register a scope.
  # @return [Array<Porolog::Rule>] the Predicate's rule.
  def <<(rule)
    @rules << rule
  end
  
  # A pretty print String of the Predicate.
  # @return [String] the Predicate as a String.
  def inspect
    lines = []
    
    if @rules.size == 1
      lines << "#{@name}:-#{@rules.first.inspect}"
    else
      lines << "#{@name}:-"
      @rules.each do |rule|
        lines << rule.inspect
      end
    end
      
    lines.join("\n")
  end
  
  # Return a builtin Predicate based on its key.
  # @param key [Symbol] the name (or otherwise object) used to register a scope.
  # @return [Porolog::Predicate] a Predicate with the next id based on the key.
  def self.builtin(key)
    @builtin_predicate_ids[key] ||= 0
    @builtin_predicate_ids[key]  += 1
    
    self.new("_#{key}_#{@builtin_predicate_ids[key]}")
  end
  
end

Class Method Details

.[](name) ⇒ Porolog::Predicate

Looks up a Predicate in the current scope by its name.

Parameters:

  • name (Object) —

    the name (or otherwise object) used to register a scope.

Returns:



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# File 'lib/porolog/predicate.rb', line 59

def self.[](name)
  @@current_scope[name]
end

.builtin(key) ⇒ Porolog::Predicate

Return a builtin Predicate based on its key.

Parameters:

  • key (Symbol) —

    the name (or otherwise object) used to register a scope.

Returns:



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# File 'lib/porolog/predicate.rb', line 125

def self.builtin(key)
  @builtin_predicate_ids[key] ||= 0
  @builtin_predicate_ids[key]  += 1
  
  self.new("_#{key}_#{@builtin_predicate_ids[key]}")
end

.new(*args) ⇒ Porolog::Predicate

Creates a new Predicate, or returns an existing Predicate if one already exists with the given name in the current scope.

Returns:



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# File 'lib/porolog/predicate.rb', line 80

def self.new(*args)
  name, _ = *args
  scope[name.to_sym] || super
end

.reset ⇒ Porolog::Scope

Resets the current scope to default and deregisters builtin predicates.

Returns:



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# File 'lib/porolog/predicate.rb', line 51

def self.reset
  scope(:default)
  @builtin_predicate_ids = {}
end

.scope(scope_name = nil) ⇒ Porolog::Scope

Returns the current scope, or sets the current scope if a paramter is provided (creating the new scope if necessary).

Parameters:

  • scope_name (Object) (defaults to: nil) —

    the name (or otherwise object) used to register a scope.

Returns:



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# File 'lib/porolog/predicate.rb', line 31

def self.scope(scope_name = nil)
  if scope_name
    @@current_scope = Scope[scope_name] || Scope.new(scope_name)
  else
    @@current_scope
  end
end

.scope=(scope_name) ⇒ Porolog::Scope

Sets the current scope (creating the new scope if necessary.

Parameters:

  • scope_name (Object) —

    the name (or otherwise object) used to register a scope.

Returns:



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# File 'lib/porolog/predicate.rb', line 42

def self.scope=(scope_name)
  if scope_name
    @@current_scope = Scope[scope_name] || Scope.new(scope_name)
  end
  @@current_scope
end

Instance Method Details

#<<(rule) ⇒ Array<Porolog::Rule>

Add a Rule to the Predicate.

Parameters:

  • rule (Object) —

    the name (or otherwise object) used to register a scope.

Returns:

  • (Array<Porolog::Rule>) —

    the Predicate’s rule.



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# File 'lib/porolog/predicate.rb', line 101

def <<(rule)
  @rules << rule
end

#arguments(*args) ⇒ Object

Create Arguments for the Predicate.



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# File 'lib/porolog/predicate.rb', line 94

def arguments(*args)
  Arguments.new(self,args)
end

#call(*args) ⇒ Porolog::Arguments

Create Arguments for the Predicate. Provides the syntax options:

  • p.(x,y,z)

Returns:

  • (Porolog::Arguments) —

    Arguments of the Predicate with the given arguments.



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# File 'lib/porolog/predicate.rb', line 89

def call(*args)
  Arguments.new(self,args)
end

#inspect ⇒ String

A pretty print String of the Predicate.

Returns:

  • (String) —

    the Predicate as a String.



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# File 'lib/porolog/predicate.rb', line 107

def inspect
  lines = []
  
  if @rules.size == 1
    lines << "#{@name}:-#{@rules.first.inspect}"
  else
    lines << "#{@name}:-"
    @rules.each do |rule|
      lines << rule.inspect
    end
  end
    
  lines.join("\n")
end