Class: Factbase::Head

Inherits:
TermBase show all
Defined in:
lib/factbase/terms/head.rb

Overview

It retrieves the first N results from a query.

Instance Method Summary collapse

Methods included from TermShared

#to_s

Constructor Details

#initialize(operands) ⇒ Head

Constructor.

Parameters:

  • operands (Array) —

    Operands



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# File 'lib/factbase/terms/head.rb', line 12

def initialize(operands)
  super()
  @operands = operands
  @op = 'head'
end

Instance Method Details

#evaluate(_fact, _maps, _fb) ⇒ Boolean

Evaluate term on a fact.

Parameters:

Returns:



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# File 'lib/factbase/terms/head.rb', line 23

def evaluate(_fact, _maps, _fb)
  true
end

#predict(maps, fb, params) ⇒ Object 



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# File 'lib/factbase/terms/head.rb', line 27

def predict(maps, fb, params)
  assert_args(2)
  max = @operands[0]
  raise "An integer is expected as first argument of '#{@op}'" unless max.is_a?(Integer)
  term = @operands[1]
  raise "A term is expected, but '#{term}' provided" unless term.is_a?(Factbase::Term)
  fb.query(term, maps).each(fb, params).to_a
    .take(max)
    .map { |m| m.all_properties.to_h { |k| [k, m[k]] } }
end