Class: Factbase::Term

Inherits:
TermBase 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({ '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.

It is NOT thread-safe!

Author

Yegor Bugayenko (yegor256@gmail.com)

Copyright

Copyright © 2024-2026 Yegor Bugayenko

License

MIT

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from TermBase

#to_s

Constructor Details

#initialize(operator, operands) ⇒ Term

Ctor.

Parameters:

  • operator (Symbol) —

    Operator

  • operands (Array) —

    Operands



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# File 'lib/factbase/term.rb', line 104

def initialize(operator, operands)
  super()
  @op = operator
  @operands = operands
  @terms = {
    unique: Factbase::Unique.new(operands),
    prev: Factbase::Prev.new(operands),
    concat: Factbase::Concat.new(operands),
    sprintf: Factbase::Sprintf.new(operands),
    matches: Factbase::Matches.new(operands),
    contains: Factbase::Contains.new(operands),
    starts_with: Factbase::StartsWith.new(operands),
    ends_with: Factbase::EndsWith.new(operands),
    traced: Factbase::Traced.new(operands),
    assert: Factbase::Assert.new(operands),
    env: Factbase::Env.new(operands),
    defn: Factbase::Defn.new(operands),
    undef: Factbase::Undef.new(operands),
    as: Factbase::As.new(operands),
    join: Factbase::Join.new(operands),
    exists: Factbase::Exists.new(operands),
    absent: Factbase::Absent.new(operands),
    size: Factbase::Size.new(operands),
    type: Factbase::Type.new(operands),
    nil: Factbase::Nil.new(operands),
    many: Factbase::Many.new(operands),
    one: Factbase::One.new(operands),
    to_string: Factbase::ToString.new(operands),
    to_integer: Factbase::ToInteger.new(operands),
    to_float: Factbase::ToFloat.new(operands),
    to_time: Factbase::ToTime.new(operands),
    sorted: Factbase::Sorted.new(operands),
    inverted: Factbase::Inverted.new(operands),
    head: Factbase::Head.new(operands),
    plus: Factbase::Plus.new(operands),
    minus: Factbase::Minus.new(operands),
    times: Factbase::Times.new(operands),
    div: Factbase::Div.new(operands),
    zero: Factbase::Zero.new(operands),
    eq: Factbase::Eq.new(operands),
    lt: Factbase::Lt.new(operands),
    lte: Factbase::Lte.new(operands),
    gt: Factbase::Gt.new(operands),
    gte: Factbase::Gte.new(operands),
    always: Factbase::Always.new(operands),
    never: Factbase::Never.new(operands),
    not: Factbase::Not.new(operands),
    or: Factbase::Or.new(operands),
    and: Factbase::And.new(operands),
    when: Factbase::When.new(operands),
    either: Factbase::Either.new(operands),
    count: Factbase::Count.new(operands),
    first: Factbase::First.new(operands),
    nth: Factbase::Nth.new(operands),
    sum: Factbase::Sum.new(operands),
    agg: Factbase::Agg.new(operands),
    empty: Factbase::Empty.new(operands),
    min: Factbase::Min.new(operands),
    max: Factbase::Max.new(operands)
  }
end

Instance Attribute Details

#op ⇒ Symbol (readonly)

The operator of this term

Returns:

  • (Symbol) —

    The operator



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# File 'lib/factbase/term.rb', line 95

def op
  @op
end

#operands ⇒ Array (readonly)

The operands of this term

Returns:

  • (Array) —

    The operands



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# File 'lib/factbase/term.rb', line 99

def operands
  @operands
end

Instance Method Details

#abstract? ⇒ Boolean

Does it have any variables (+$foo+, for example) inside?

Returns:



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# File 'lib/factbase/term.rb', line 254

def abstract?
  @operands.each do |o|
    return true if o.is_a?(Factbase::Term) && o.abstract?
    return true if o.is_a?(Symbol) && o.to_s.start_with?('$')
  end
  false
end

#at(fact, maps, fb) ⇒ Object 



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# File 'lib/factbase/term.rb', line 262

def at(fact, maps, fb)
  assert_args(2)
  i = _values(0, fact, maps, fb)
  raise "Too many values (#{i.size}) at first position, one expected" unless i.size == 1
  i = i[0]
  return nil if i.nil?
  v = _values(1, fact, maps, fb)
  return nil if v.nil?
  v[i]
end

#evaluate(fact, maps, fb) ⇒ Object

Evaluate term on a fact

Parameters:

Returns:

  • (Object) —

    The result of evaluation



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# File 'lib/factbase/term.rb', line 209

def evaluate(fact, maps, fb)
  if @terms.key?(@op)
    @terms[@op].evaluate(fact, maps, fb)
  else
    send(@op, fact, maps, fb)
  end
rescue NoMethodError => e
  raise "Probably the term '#{@op}' is not defined at #{self}: #{e.message}"
rescue StandardError => e
  raise "#{e.message.inspect} at #{self} at #{e.backtrace[0]}"
end

#predict(maps, fb, params) ⇒ Array<Hash>

Try to predict which facts from the provided list should be evaluated. If no prediction can be made, the same list is returned.

Parameters:

  • maps (Array<Hash>, Factbase::Taped, Factbase::LazyTaped) —

    Records to iterate, maybe

  • params (Hash) —

    Params to use (keys must be strings, not symbols, with values as arrays)

Returns:

  • (Array<Hash>) —

    Records to iterate



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# File 'lib/factbase/term.rb', line 188

def predict(maps, fb, params)
  m = :"#{@op}_predict"
  if @terms.key?(@op)
    t = @terms[@op]
    if t.respond_to?(:predict)
      t.predict(maps, fb, params)
    else
      maps
    end
  elsif respond_to?(m)
    send(m, maps, fb, params)
  else
    maps
  end
end

#redress!(type, **args) ⇒ Object

Extend it with the module.

Parameters:

  • type (Module) —

    The type to extend with

  • args (Hash) —

    Attributes to set



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# File 'lib/factbase/term.rb', line 169

def redress!(type, **args)
  extend type

  args.each { |k, v| send(:instance_variable_set, :"@#{k}", v) }
  @operands.map do |op|
    if op.is_a?(Factbase::Term)
      op.redress!(type, **args)
    else
      op
    end
  end
end

#simplify ⇒ Factbase::Term

Simplify it if possible.

Returns:



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# File 'lib/factbase/term.rb', line 223

def simplify
  if @terms.key?(@op) && @terms[@op].respond_to?(:simplify)
    @terms[@op].simplify
  else
    m = "#{@op}_simplify"
    if respond_to?(m, true)
      send(m)
    else
      self
    end
  end
end

#static? ⇒ Boolean

Does it have any dependencies on a fact?

If a term is static, it will return the same value for evaluate, no matter what is the fact given.

Returns:



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# File 'lib/factbase/term.rb', line 242

def static?
  return true if @op == :agg
  @operands.each do |o|
    return false if o.is_a?(Factbase::Term) && !o.static?
    return false if o.is_a?(Symbol) && !o.to_s.start_with?('$')
  end
  true
end