# Command: topology::Distance

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Name:

    topology::Distance - compute distance between nodes

Synopsis:

    from_gid to_gid Distance -> double
      from_pos to_gid Distance -> double

Description:

      This function returns the distance between the position of the "from_gid"
      node or the explicitly given "from_pos" position and the position of the
      "to_gid" node. Nodes must be parts of topology layers.

      The "from" position is projected into the layer of the "to_gid" node. If
      this layer has periodic boundary conditions (EdgeWrap is true), then the
      shortest distance is returned, taking into account the
      periodicity. Fixed grid layers are in this case extended so that the
      nodes at the edges of the layer have a distance of one grid unit when
      wrapped.

      Example:

      topology using
      << /rows 5
      /columns 4
      /elements /iaf_psc_alpha
      >> CreateLayer ;

      4 5	 Distance
      [0.2 0.3] 5 Distance

Parameters:

      from_gid  	- int, gid of node in a topology layer
      from_pos  	- double vector, position in layer
      to_gid		- int, gid of node in a topology layer

      Returns:
      double	- distance between nodes or given position and node

Author:

    Hans E Plesser, Kittel Austvoll

      See also: Displacement, GetPosition

Source:

    /opt/conda/conda-bld/nest_1510213973486/work/nest-2.14.0/topology/topologymodule.cpp

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