recursion in NetLogo - recursion

Question

In NetLogo 6.1.1 I have one breed (rangers) looking for another breed (snares) in green patches (bush).
The behaviour that I can't get is this:
if a snare is found, remove the snare with 80% success rate; then
repeat the same procedure (hotspot-search; recursive call).
if the snare is not found (20% probability) then repeat the same
procedure (hotspot-search; the commented out section -> causes an endless loop) 5 times.
if no snares are removed in these 5 times, resume normal behaviour (move by random right turn and forward 1).
How can I do this?
;; globals =========================
breed [rangers ranger]
breed [snares snare]
rangers-own [snare-found?]
;; initialise ========================
to setup
resize-world -4 4 -4 4
clear-all
create-rangers 1 [set color blue]
ask patches [
if random 100 < 20 [set pcolor green]]
ask patches with [pcolor = green] [
sprout-snares random 5]
ask snares [
set size 0.5
set shape "dot"
fd 0.25
]
reset-ticks
end
;; main ==================================
to go
ask rangers [
rt random 181 - 90
fd 1
if any? snares-here [hotspot-search]
hotspot-search
]
end
;; functions ===============================
to hotspot-search
move-to patch-here
let target one-of snares-here
if (random 100 < 20) and (target != nobody) [
ask target [die]
set snare-found? true
hotspot-search
]
;;if snare-found? = true [
;; repeat 5 [hotspot-search]
;;]
end

Answer 1

One observation I'd make is that if you're wanting the rangers to search 5 times at a 20% chance of success, but there is no cost for searching, like lost time or energy, you can just do a single check at a 67% chance of success (1.00 - 0.80^5) = 0.67.
But if you do need have a cost or need to track the number of searches or something like that, below is how I'd write the code. Sorry for writing from scratch rather than updating yours, I was just trying to keep things as simple as possible.
breed [ rangers ranger ]
breed [ snares snare ]
to setup
create-snares 100 [
set shape "circle"
set color blue
set size 0.5
move-to one-of patches
]
create-rangers 10 [
set color red
move-to one-of patches
]
end
to go
ask rangers [
move-to one-of neighbors4
; call our procedure with the starting limit of 5
hunt-snares 5
]
end
to hunt-snares [ search-limit ]
; the recursive base case is search-limit of 0
if ( search-limit > 0 ) [
; can only find a snare if one exists here
ifelse random 100 < 20 and any? snares-here [
; found one
ifelse random 100 < 80 [
; disabled
ask one-of snares-here [ die ]
; restart the search
hunt-snares 5
] [
; we found a snare but failed to disable it, unclear what to do?
hunt-snares 5
]
] [
; failed to find one, move towards the base case
hunt-snares (search-limit - 1)
]
]
end
Edit to add: Sorry, I thought your original code was more complicated, it actually looks relatively simple and I probably should've just modified your version. The reason your hotspot-search procedure is going into an infinite loop is because snare-found? is never set to false anywhere in your code. The typical way to handle recursion is to have one parameter of the recursive procedure progress towards a base case where the last recursive call can quit and the whole chain of calls will end, too.
In this case we have two complications: 1) an implicit base-case that isn't a parameter - that there are still snares on the patch to try to disarm, and 2) that we can reset our parameter farther from the base case, knowing that item 1 means we won't loop over.