class Sequel::SQL::BooleanExpression

Take pairs of values (e.g. a hash or array of two element arrays) and converts it to a BooleanExpression. The operator and args used depends on the case of the right (2nd) argument:

• 0..10 - left >= 0 AND left <= 10

• 1,2

  • left IN (1,2)

• nil - left IS NULL

• true - left IS TRUE

• false - left IS FALSE

• /as/ - left ~ 'as'

• :blah - left = blah

• 'blah' - left = 'blah'

If multiple arguments are given, they are joined with the op given (AND by default, OR possible). If negate is set to true, all subexpressions are inverted before used. Therefore, the following expressions are equivalent:

~from_value_pairs(hash)
from_value_pairs(hash, :OR, true)

# File lib/sequel/sql.rb, line 887
def self.from_value_pairs(pairs, op=:AND, negate=false)
  pairs = pairs.collect do |l,r|
    ce = case r
    when Range
      new(:AND, new(:>=, l, r.begin), new(r.exclude_end? ? :< : :<=, l, r.end))
    when ::Array, ::Sequel::Dataset
      new(:IN, l, r)
    when NegativeBooleanConstant
      new(:"IS NOT", l, r.constant)
    when BooleanConstant
      new(:IS, l, r.constant)
    when NilClass, TrueClass, FalseClass
      new(:IS, l, r)
    when Regexp
      StringExpression.like(l, r)
    else
      new(:'=', l, r)
    end
    negate ? invert(ce) : ce
  end
  pairs.length == 1 ? pairs.at(0) : new(op, *pairs)
end

Invert the expression, if possible. If the expression cannot be inverted, raise an error. An inverted expression should match everything that the uninverted expression did not match, and vice-versa, except for possible issues with SQL NULL (i.e. 1 == NULL is NULL and 1 != NULL is also NULL).

BooleanExpression.invert(:a) # NOT "a"

# File lib/sequel/sql.rb, line 916
def self.invert(ce)
  case ce
  when BooleanExpression
    case op = ce.op
    when :AND, :OR
      BooleanExpression.new(OPERTATOR_INVERSIONS[op], *ce.args.collect{|a| BooleanExpression.invert(a)})
    else
      BooleanExpression.new(OPERTATOR_INVERSIONS[op], *ce.args.dup)
    end
  when StringExpression, NumericExpression
    raise(Sequel::Error, "cannot invert #{ce.inspect}")
  when Constant
    CONSTANT_INVERSIONS[ce] || raise(Sequel::Error, "cannot invert #{ce.inspect}")
  else
    BooleanExpression.new(:NOT, ce)
  end
end