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module LD::Patch::Algebra
##
# The LD Patch `cut` operator.
#
# The Cut operation is recursively remove triples from some starting node.
#
# @example
# (cut ?a)
#
class Cut < SPARQL::Algebra::Operator::Unary
include SPARQL::Algebra::Update
include SPARQL::Algebra::Evaluatable
NAME = :cut
##
# Executes this upate on the given `writable` graph or repository.
#
# @param [RDF::Queryable] queryable
# the graph or repository to write
# @param [Hash{Symbol => Object}] options
# any additional options
# @return [RDF::Query::Solutions] A single solution including passed bindings with `var` bound to the solution.
# @raise [IOError]
# If no triples are identified, or the operand is an unbound variable or the operand is an unbound variable.
# @see http://www.w3.org/TR/sparql11-update/
def execute(queryable, options = {})
debug(options) {"Cut"}
bindings = options.fetch(:bindings)
solution = bindings.first
var = operand(0)
# Bind variable
raise LD::Patch::Error.new("Operand uses unbound variable #{var.inspect}", code: 400) unless solution.bound?(var)
var = solution[var]
cut_count = 0
# Get triples to delete using consice bounded description
queryable.concise_bounded_description(var) do |statement|
queryable.delete(statement)
cut_count += 1
end
# Also delete triples having var in the object position
queryable.query(object: var).each do |statement|
queryable.delete(statement)
cut_count += 1
end
raise LD::Patch::Error, "Cut removed no triples" unless cut_count > 0
bindings
end
end
end
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12 entries across 12 versions & 1 rubygems