This commands replaces the apply command in prior versions of SpecTcl. This replacement was done because the apply command was added to the Tcl core command set in version 8.5 and by now there are Tcl packages and scripts internal to the Tcl implementation that rely on that command and fail if SpecTcl overrides it.
The implementation of the applygate command is wrapped in
a CMPITclPackagedCommand.
Ultimately the SpecTcl API is used to perform gate applications. If there is a histogrammer object, as there is in the MPI_EVENT_SINK_RANK it is used to apply the gate. If not, the spectrum is looked up in the mirrored spectrum dictionary and asked to apply the gate.
When listing gates; this command only operates in the MPI_EVENT_SINK_RANK process. It enumerates spectra that match the optional pattern (which defaults to * matching all spectra). Each spectrum is asked about the gate applied to it and returns the list as the result with a status of TCL_OK. All other ranks return a status of TCL_OK but an empty result. Since the overall command result is the longest of all resuts, the gate application list is the ultimate result of the command.