NetLogo: Subtract One Patch-set From Another -

im trying create patch-set without having define each patch in list individually. however, in order need subtract 1 patch-set another. in model, patches own o2. have few selected patches in value o2 should not change. create patch-set patches pxcor = max-pxcor exclude these patches should hold o2 constant. have tried subtracting patch-sets, got error message saying -expected input number, got patch agentset instead. have tried setting patch-set lists, , using remove command modify list. however, presents problem when ask list perform something, error ask expected agent or agentset, got list instead.

below relevant code try build patch-set:

set ns1 (patch-set patch -8 -5 6 patch -8 -5 -5 patch -8 6 6 patch -8 6 -5  patch 8 -5 6 patch 8 -5 -5 patch 8 6 6 patch 8 6 -5)  set ns2 (patch-set patch -8 0 6 patch -8 0 -5 patch 8 0 6 patch 8 0 -5  )   set ns3 (patch-set patch -4 -5 6 patch -4 -5 -5 patch 4 -5 6 patch 4 -5 -5 patch -4 6 6 patch -4 6 -5 patch 4 6 6 patch 4 6 -5)  set ns4 (patch-set patch -4 0 6 patch -4 0 -5 patch 4 0 6 patch 4 0 -5 )   set ns5 (patch-set patch -8 0 0 patch 8 0 0 )                  set ns6 (patch-set patch -8 -5 0 patch -8 6 0 patch 8 -5 0 patch 8 6 0 )       set ns7 (patch-set patch -4 -5 0 patch -4 6 0 patch 4 -5 0 patch 4 6 0   )    set ns8 (patch-set patch 0 0 6 patch 0 0 -5 )              set ns9 (patch-set patch 0 -5 6 patch 0 -5 -5 patch 0 6 6 patch 0 6 -5) set ns10 (patch-set patch 0 -5 0 patch 0 6 0 )              set ns11 patch 0 0 0                           set ns12 (patch-set patch -4 0 0 patch 4 0 0 )               set femnodes (sentence ns1 ns2 ns3 ns4 ns5 ns6 ns7 ns8 ns9 ns10 ns11 ns12)   set xmaxmin (list (patch-set patches [ pxcor = min-pxcor] patches [ pxcor = max-pxcor])) set lateral remove femnodes xmaxmin set ymaxmin (list (patch-set patches [ pycor = min-pycor ] patches [ pycor = max-pycor ])) set fb remove femnodes ymaxmin set zmaxmin (list (patch-set patches [ pzcor = min-pzcor ] patches [ pzcor = max-pzcor ])) set tp remove femnodes zmaxmin 

i assume femnodes contains patches constant o2, correct? if so, can following:

patches [ pxcor = max-pxcor , not member? self femnodes ] 

to patches pxcor = max-pxcor not in femnodes.

so, think want xmaxmin defined follows:

set xmaxmin patches [ (pxcor = min-pxcor or pxcor = max-pxcor) , not member? self femnodes ] 

for general patch-set difference, can use:

to-report patch-set-difference [ set1 set2 ]   report set1 [ not member? self set2 ] end 

but think definition of xmaxmin gave more strategy you'll want use.