NetLogo: Apply set [variable] from sub-procedure to global process? - netlogo

Question

I want to simulate reproduction process of turtles in time when single patch can by used only once. If the patch is red and ticks mod 50 = 0 then turtles-here (on this patch) hatch new 10 turtles. Every patch can be used only once during the whole simulation run.
Please, how can I include this condition into my code? I tried simple to change patch color to green with hope that the next hatching process will run only with red ones. However next time step NetLogo doesn't keep this patch green but changes it back to red. Thus my reproduction run from the same patch.
Any suggestions will be highly appreciated
The part of my code:
to go
if ticks mod 50 = 0 [ask patches with [pcolor= red] [reproduce] ]
end
to reproduce
ask one-of turtles-here
[hatch 10 ;
die]
; set pcolor green - change infestlev from 2 to 5 only for specific tick, not for the rest of the simulation
end

Answer 1

The code you have should work fine. In your description, you state that the colour turns back to red - so that's why this code isn't working, somewhere else you have a colouring procedure. Alternatively, if you don't want to rely on colour (or if you want colours to mean something else), then you can add a variable to each patch to keep track of whether it has already reproduced.
patches-own [reproduced?]
to setup
...
ask patches [set reproduced? FALSE]
...
end
to go
if ticks mod 50 = 0 [ask patches with [not reproduced?] [reproduce] ]
end
to reproduce
ask one-of turtles-here
[ hatch 10
die ]
set reproduced? TRUE
end
Just as a general comment, it is a little odd to ask the patch to reproduce when what you are really trying to do is have the turtle on a patch reproduce. Logically you are saying that once one turtle on a patch has reproduced, then no other turtle on that patch can ever reproduce. If the reproduction is truly governed by the patch, it would be more usual to use sprout instead of hatch. That gets you code that looks like this:
to reproduce
sprout 10 [ any commands you want the new turtles to do ]
set reproduced? TRUE
end

Answer 2

My final working code with steps (available here: http://ulozto.cz/xRqtDDfV/timing-of-turtle-sprout-nlogo):
setup turtles
if turtle touch red patch, turn this patch blue
at the same time - tick 10 -> sprout from every blue patch 10 nwe turtles
every patch can be used only once during simulation run (turn red, assured by reproduced? variable)
enter code here
patches-own [reproduced?]
to setup
clear-all
setup-turtles
setup-patches
change-color
reset-ticks
end
to setup-patches
ask patches [set reproduced? FALSE]
ask patches [set pcolor green]
ask n-of 80 patches [set pcolor red] ; identify turles which could be a source for new turtles
end
to setup-turtles
crt 1
ask turtles [set color yellow]
end
to go
if ticks mod 10 = 0 [
ask patches with [(pcolor = blue) and not (reproduced?)]
[reproduce] ; set reproduction to every 10 ticks for all blue patches
]
move-turtles
change-color
tick
end
to move-turtles
ask turtles [fd 1]
end
to change-color ; if turtle touch red patch, red turns blue
ask turtles [if pcolor = red
[set pcolor blue]
]
end
to reproduce ; sprout 10 new turtles from blue patches at defined time step (multiply of 10 ticks)
sprout 10
set reproduced? TRUE
end