def numeric(expr):
"""
return a number from a literal
http://www.w3.org/TR/xpath20/#promotion
or TypeError
"""
if not isinstance(expr, Literal):
raise SPARQLTypeError("%r is not a literal!" % expr)
if expr.datatype not in (
XSD.float,
XSD.double,
XSD.decimal,
XSD.integer,
XSD.nonPositiveInteger,
XSD.negativeInteger,
XSD.nonNegativeInteger,
XSD.positiveInteger,
XSD.unsignedLong,
XSD.unsignedInt,
XSD.unsignedShort,
XSD.unsignedByte,
XSD.long,
XSD.int,
XSD.short,
XSD.byte,
):
raise SPARQLTypeError("%r does not have a numeric datatype!" % expr)
return expr.toPython()
def EBV(rt):
"""
Effective Boolean Value (EBV)
* If the argument is a typed literal with a datatype of xsd:boolean,
the EBV is the value of that argument.
* If the argument is a plain literal or a typed literal with a
datatype of xsd:string, the EBV is false if the operand value
has zero length; otherwise the EBV is true.
* If the argument is a numeric type or a typed literal with a datatype
derived from a numeric type, the EBV is false if the operand value is
NaN or is numerically equal to zero; otherwise the EBV is true.
* All other arguments, including unbound arguments, produce a type error.
"""
if isinstance(rt, Literal):
if rt.datatype == XSD.boolean:
return rt.toPython()
elif rt.datatype == XSD.string or rt.datatype is None:
return len(rt) > 0
else:
pyRT = rt.toPython()
if isinstance(pyRT, Literal):
# Type error, see: http://www.w3.org/TR/rdf-sparql-query/#ebv
raise SPARQLTypeError(
"http://www.w3.org/TR/rdf-sparql-query/#ebv - ' + \
'Could not determine the EBV for : %r"
% rt
)
else:
return bool(pyRT)
else:
raise SPARQLTypeError(
"http://www.w3.org/TR/rdf-sparql-query/#ebv - ' + \
'Only literals have Boolean values! %r"
% rt
)