How to use sparql_read_json_result

[Wolfram Diestel]

Hello,

I don't see how to use sparql_read_json_result from sparql_client library.
My expectation was, that I can first call sparql_query and then pipe the results through sparql_read_json_result somehow, but
when my SPARQL query returns JSON (application/sparql-results+json), I get an exception instead, e.g.

sparql_set_server([ host('h2181216.stratoserver.net'),
                        port(80),
                        path('/revo/query')
                      ]).

sparql_query(
'PREFIX owl: <http://www.w3.org/2002/07/owl#> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX skos: <http://www.w3.org/2004/02/skos/core#> PREFIX voko: <http://purl.org/net/voko#> PREFIX revo: <http://purl.org/net/voko/revo#>SELECT * WHERE { {?subject voko:trd "Borage"@en} UNION {?subject voko:trd "borage"@en}. ?subject voko:trd ?traduko }',Result,[]).

ERROR: Domain error: `sparql_result_document' expected, found `application/sparql-results+json' ({
  "head": {
    "vars": [ "subject" , "traduko" ]
  } ,
  "results": {
    "bindings": [
      {
        "subject": { "type": "uri" , "value": "http://purl.org/net/voko/revo#borag_0o" } ,
        "traduko": { "type": "literal" , "xml:lang": "nl" , "value": "bernagie" }
      } ,
      {
...


Could someone hint me?

Thank you,
   Wolfram.

[Wolfram Diestel]

I found a workaround catching the domain_error which contains the full reply as a string and than transfering the reply via a memory file to sparql_read_json_result, but that doesn't look like the intended use.