Class: Predicate

Inherits:
Object
  • Object
show all
Extended by:
Factory
Defined in:
lib/predicate.rb,
lib/predicate/sequel.rb,
lib/predicate/factory.rb,
lib/predicate/grammar.rb,
lib/predicate/version.rb,
lib/predicate/nodes/eq.rb,
lib/predicate/nodes/gt.rb,
lib/predicate/nodes/in.rb,
lib/predicate/nodes/lt.rb,
lib/predicate/nodes/or.rb,
lib/predicate/nodes/and.rb,
lib/predicate/nodes/gte.rb,
lib/predicate/nodes/lte.rb,
lib/predicate/nodes/neq.rb,
lib/predicate/nodes/not.rb,
lib/predicate/nodes/expr.rb,
lib/predicate/nodes/match.rb,
lib/predicate/nodes/native.rb,
lib/predicate/nodes/opaque.rb,
lib/predicate/nodes/literal.rb,
lib/predicate/nodes/intersect.rb,
lib/predicate/nodes/tautology.rb,
lib/predicate/processors/to_s.rb,
lib/predicate/nodes/identifier.rb,
lib/predicate/nodes/nadic_bool.rb,
lib/predicate/sequel/to_sequel.rb,
lib/predicate/nodes/dyadic_comp.rb,
lib/predicate/processors/renamer.rb,
lib/predicate/nodes/contradiction.rb,
lib/predicate/processors/qualifier.rb,
lib/predicate/nodes/qualified_identifier.rb

Defined Under Namespace

Modules: And, Contradiction, DyadicComp, Eq, Expr, Factory, Grammar, Gt, Gte, Identifier, In, Intersect, Literal, Lt, Lte, Match, NadicBool, Native, Neq, Not, Opaque, Or, QualifiedIdentifier, Tautology, Version Classes: NotSupportedError, Qualifier, Renamer, ToS, ToSequel

Constant Summary collapse

TupleLike = 
->(t){ t.is_a?(Hash) }
SexprLike = 
->(x) { x.is_a?(Array) && x.first.is_a?(Symbol) }
VERSION = 
"#{Version::MAJOR}.#{Version::MINOR}.#{Version::TINY}"

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Factory

and, between, comp, contradiction, from_hash, identifier, in, intersect, literal, match, native, not, opaque, or, qualified_identifier, tautology

Constructor Details

#initialize(sexpr) ⇒ Predicate

Returns a new instance of Predicate.



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# File 'lib/predicate.rb', line 14

def initialize(sexpr)
  @sexpr = sexpr
end

Instance Attribute Details

#sexpr ⇒ Object (readonly) Also known as: expr

Returns the value of attribute sexpr.



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# File 'lib/predicate.rb', line 17

def sexpr
  @sexpr
end

Class Method Details

.coerce(arg) ⇒ Object Also known as: parse 



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# File 'lib/predicate.rb', line 23

def coerce(arg)
  case arg
  when Predicate   then arg
  when TrueClass   then tautology
  when FalseClass  then contradiction
  when Symbol      then identifier(arg)
  when Proc        then native(arg)
  when Hash        then from_hash(arg)
  else
    raise ArgumentError, "Unable to coerce `#{arg}` to a predicate"
  end
end

Instance Method Details

#! ⇒ Object 



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# File 'lib/predicate.rb', line 81

def !
  Predicate.new(!expr)
end

#&(other) ⇒ Object 



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# File 'lib/predicate.rb', line 69

def &(other)
  return self  if other.tautology? or other==self
  return other if tautology?
  Predicate.new(expr & other.expr)
end

#==(other) ⇒ Object Also known as: eql? 



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# File 'lib/predicate.rb', line 122

def ==(other)
  other.is_a?(Predicate) && (other.expr==expr)
end

#and_split(attr_list) ⇒ Object

Splits this predicate, say P, as too predicates P1 & P2 such that ‘P <=> P1 & P2` and P2 makes no reference to any attribute in `attr_list`.



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# File 'lib/predicate.rb', line 104

def and_split(attr_list)
  expr.and_split(attr_list).map{|e| Predicate.new(e)}
end

#attr_split ⇒ Object

Returns a hash ‘(attr -> Pattr)` associating attribute names to predicates, so that each predicate `Pattr` only makes reference to the corresponding attribute name `attr`, while the conjunction of `Pattr`s is still equivalent to the original predicate.

A ‘nil` key may map a predicate that still makes references to more than one attribute.



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# File 'lib/predicate.rb', line 116

def attr_split
  expr.attr_split.each_pair.each_with_object({}) do |(k,v),h|
    h[k] = Predicate.new(v)
  end
end

#call(tuple) ⇒ Object 



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# File 'lib/predicate.rb', line 97

def call(tuple)
  expr.evaluate(tuple)
end

#constant_variables ⇒ Object 



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# File 'lib/predicate.rb', line 61

def constant_variables
  expr.constant_variables
end

#constants ⇒ Object 



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# File 'lib/predicate.rb', line 65

def constants
  expr.constants
end

#contradiction? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/predicate.rb', line 53

def contradiction?
  expr.contradiction?
end

#evaluate(tuple) ⇒ Object 



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# File 'lib/predicate.rb', line 93

def evaluate(tuple)
  expr.evaluate(tuple)
end

#free_variables ⇒ Object 



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# File 'lib/predicate.rb', line 57

def free_variables
  expr.free_variables
end

#hash ⇒ Object 



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# File 'lib/predicate.rb', line 127

def hash
  expr.hash
end

#native? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/predicate.rb', line 45

def native?
  Native===expr
end

#qualify(qualifier) ⇒ Object 



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# File 'lib/predicate.rb', line 85

def qualify(qualifier)
  Predicate.new(expr.qualify(qualifier))
end

#rename(renaming) ⇒ Object 



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

def rename(renaming)
  Predicate.new(expr.rename(renaming))
end

#tautology? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/predicate.rb', line 49

def tautology?
  expr.tautology?
end

#to_s(scope = nil) ⇒ Object 



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# File 'lib/predicate.rb', line 131

def to_s(scope = nil)
  expr.to_s(scope)
end

#to_sequel ⇒ Object

module Expr



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# File 'lib/predicate/sequel.rb', line 11

def to_sequel
  expr.to_sequel
end

#|(other) ⇒ Object 



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# File 'lib/predicate.rb', line 75

def |(other)
  return self  if other.contradiction? or other==self
  return other if contradiction?
  Predicate.new(expr | other.expr)
end