Class: Predicate

Inherits:
Object
  • Object
show all
Extended by:
Factory, Sugar
Defined in:
lib/predicate.rb,
lib/predicate/dsl.rb,
lib/predicate/sugar.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/var.rb,
lib/predicate/nodes/expr.rb,
lib/predicate/nodes/empty.rb,
lib/predicate/nodes/match.rb,
lib/predicate/placeholder.rb,
lib/predicate/nodes/native.rb,
lib/predicate/nodes/opaque.rb,
lib/predicate/nodes/set_op.rb,
lib/predicate/nodes/subset.rb,
lib/predicate/nodes/literal.rb,
lib/predicate/nodes/has_size.rb,
lib/predicate/nodes/superset.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/nodes/unary_func.rb,
lib/predicate/sequel/to_sequel.rb,
lib/predicate/nodes/binary_func.rb,
lib/predicate/nodes/dyadic_comp.rb,
lib/predicate/processors/binder.rb,
lib/predicate/processors/renamer.rb,
lib/predicate/nodes/contradiction.rb,
lib/predicate/processors/qualifier.rb,
lib/predicate/processors/unqualifier.rb,
lib/predicate/nodes/qualified_identifier.rb

Defined Under Namespace

Modules: And, BinaryFunc, Contradiction, DyadicComp, Empty, Eq, Expr, Factory, Grammar, Gt, Gte, HasSize, Identifier, In, Intersect, Literal, Lt, Lte, Match, NadicBool, Native, Neq, Not, Opaque, Or, QualifiedIdentifier, SetOp, Subset, Sugar, Superset, Tautology, UnaryFunc, Var, Version Classes: Binder, Dsl, Error, NotSupportedError, Placeholder, Qualifier, Renamer, ToS, ToSequel, TypeError, UnboundError, Unqualifier

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 Sugar

between, is_null, match, max_size, min_size

Methods included from Factory

and, comp, contradiction, empty, from_hash, has_size, identifier, in, literal, match, native, not, opaque, or, placeholder, qualified_identifier, tautology, var, vars

Constructor Details

#initialize(sexpr) ⇒ Predicate

Returns a new instance of Predicate.



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# File 'lib/predicate.rb', line 20

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 23

def sexpr
  @sexpr
end

Class Method Details

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



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# File 'lib/predicate.rb', line 30

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

.currying(var = var(".", :dig), &bl) ⇒ Object 



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# File 'lib/predicate.rb', line 48

def currying(var = var(".", :dig), &bl)
  Predicate::Dsl.new(var, true).instance_eval(&bl)
end

.dsl(var = var(".", :dig), &bl) ⇒ Object 



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# File 'lib/predicate.rb', line 44

def dsl(var = var(".", :dig), &bl)
  Predicate::Dsl.new(var, false).instance_eval(&bl)
end

Instance Method Details

#! ⇒ Object 



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# File 'lib/predicate.rb', line 96

def !
  Predicate.new(!expr)
end

#&(other) ⇒ Object 



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# File 'lib/predicate.rb', line 84

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 145

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 127

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 139

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

#bind(binding) ⇒ Object 



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# File 'lib/predicate.rb', line 112

def bind(binding)
  Predicate.new(expr.bind(binding))
end

#call(tuple) ⇒ Object 



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# File 'lib/predicate.rb', line 120

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

#constant_variables ⇒ Object 



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# File 'lib/predicate.rb', line 76

def constant_variables
  expr.constant_variables
end

#constants ⇒ Object 



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

def constants
  expr.constants
end

#contradiction? ⇒ Boolean

Returns:

  • (Boolean) 


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

def contradiction?
  expr.contradiction?
end

#evaluate(tuple) ⇒ Object 



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

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

#free_variables ⇒ Object 



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# File 'lib/predicate.rb', line 72

def free_variables
  expr.free_variables
end

#hash ⇒ Object 



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# File 'lib/predicate.rb', line 150

def hash
  expr.hash
end

#native? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/predicate.rb', line 60

def native?
  Native===expr
end

#qualify(qualifier) ⇒ Object 



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# File 'lib/predicate.rb', line 100

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

#rename(renaming) ⇒ Object 



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# File 'lib/predicate.rb', line 108

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

#tautology? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/predicate.rb', line 64

def tautology?
  expr.tautology?
end

#to_hash ⇒ Object

If possible, converts this predicate back to a ‘{ attr: value, … }` hash. Raises an IllegalArgumentError if the predicate cannot be represented that way.



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# File 'lib/predicate.rb', line 161

def to_hash
  expr.to_hash
end

#to_s(scope = nil) ⇒ Object 



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# File 'lib/predicate.rb', line 154

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

#unqualify ⇒ Object 



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

def unqualify
  Predicate.new(expr.unqualify)
end

#|(other) ⇒ Object 



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# File 'lib/predicate.rb', line 90

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