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std.meta.dtr

All except Query are Zdatr 2.0 additions. The meta-variables $env_qn, $env_gn and $env_ln provide access to the names of query node, the global node and the local node, respectively, for use in self-tracing theories. The nodes associated with these are defined for convenience only. Clearly, it is not possible to define a local node in this way, as it would return its own name and effectively be a constant. The names of paths in the DATR evaluation environments are defined as the atom sequences they contain, and simply accessed by means of the Idem library function adapted to the three environments.

Query:
  <> == Global
.

QnodeName:
  <> == $env_qn
.
QpathSeq:
  <>  == Qnode:<'Idem'>
.

GnodeName:
  <> == $env_gn
.

GpathSeq:
  <>  == "Idem"
.

% For local node, use $env_ln directly at the node.

LpathSeq:
  <>  == Idem
.