Class: Factbase::Term

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

Overview

Term.

This is an internal class, it is not supposed to be instantiated directly.

It is possible to use for testing directly, for example to make a term with two arguments:

require 'factbase/fact'
require 'factbase/term'
f = Factbase::Fact.new(Mutex.new, { 'foo' => [42, 256, 'Hello, world!'] })
t = Factbase::Term.new(:lt, [:foo, 50])
assert(t.evaluate(f))

The design of this class may look ugly, since it has a large number of methods, each of which corresponds to a different type of a Term. A much better design would definitely involve many classes, one per each type of a term. It’s not done this way because of an experimental nature of the project. Most probably we should keep current design intact, since it works well and is rather simple to extend (by adding new term types). Moreover, it looks like the number of possible term types is rather limited and currently we implement most of them.

Author

Yegor Bugayenko ([email protected])

Copyright

Copyright © 2024 Yegor Bugayenko

License

MIT

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(operator, operands) ⇒ Term

Ctor.

Parameters:

  • operator (Symbol) —

    Operator

  • operands (Array) —

    Operands



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# File 'lib/factbase/term.rb', line 57

def initialize(operator, operands)
  @op = operator
  @operands = operands
end

Instance Attribute Details

#op ⇒ Object (readonly)

Returns the value of attribute op.



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# File 'lib/factbase/term.rb', line 52

def op
  @op
end

#operands ⇒ Object (readonly)

Returns the value of attribute operands.



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# File 'lib/factbase/term.rb', line 52

def operands
  @operands
end

Instance Method Details

#evaluate(fact, maps) ⇒ bool

Does it match the fact?

Parameters:

Returns:

  • (bool) —

    TRUE if matches



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# File 'lib/factbase/term.rb', line 66

def evaluate(fact, maps)
  send(@op, fact, maps)
rescue NoMethodError => e
  raise "Term '#{@op}' is not defined at #{self}: #{e.message}"
rescue StandardError => e
  raise "#{e.message} at #{self} (#{e.backtrace[0]})"
end

#simplify ⇒ Factbase::Term

Simplify it if possible.

Returns:



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# File 'lib/factbase/term.rb', line 76

def simplify
  m = "#{@op}_simplify"
  if respond_to?(m, true)
    send(m)
  else
    self
  end
end

#to_s ⇒ String

Turns it into a string.

Returns:

  • (String) —

    The string of it



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# File 'lib/factbase/term.rb', line 87

def to_s
  items = []
  items << @op
  items += @operands.map do |o|
    if o.is_a?(String)
      "'#{o.gsub("'", "\\\\'").gsub('"', '\\\\"')}'"
    elsif o.is_a?(Time)
      o.utc.iso8601
    else
      o.to_s
    end
  end
  "(#{items.join(' ')})"
end