Routine Name:	getsynsrc

Description:	Returns a string which is the path of the presynaptic
		element sending the SPIKE message to the synapse of the
		postsynaptic element with the given index.

Usage:		getsynsrc postsynaptic-element index

		postsynaptic-element The synchan or derived element
		       receiving the SPIKE message from the source element.

		index  The index of the synapse on a synchan or derived element
		       whose source you want.

Example:	str src = {getsynsrc /cell/soma/Ex_chan 0}
		if (src == "input[0]/spike")
		    setfield /cell/soma/Ex_chan synapse[0].weight 10.0
		else
		    setfield /cell/soma/Ex_chan synapse[0].weight 0.0
		end

Notes:		

See also:	getsyncount, getsynindex, getsyndest, BoG chapter 17

