turtles.lg

make ".turtles array 1000
buryname ".turtles
make ".curturtle 1
buryname ".curturtle

;; turtle bookkeeping

to saveturtlestate
  .setitem turtle :.turtles turtlestate
end
bury "saveturtlestate

to markturtle
  .setitem turtle :.turtles "current
end
bury "markturtle

to checkturtle :ttl
  if emptyp item :ttl :.turtles [(throw "error se [no such turtle] :ttl)]
end
bury "checkturtle

;; turtle queries

to turtle
  op :.curturtle
end
bury "turtle

to turtlepos :ttl
  checkturtle :ttl
  if :ttl = turtle [op pos]
  op first item :ttl :.turtles
end
bury "turtlepos

to turtlestate
  op (list pos heading pen)
end
bury "turtlestate

;; changing turtles

to setturtle :ttl
  if :ttl = turtle [stop]
  checkturtle :ttl
  saveturtlestate
  make ".curturtle :ttl
  setturtlestate item :ttl :.turtles
  markturtle
end
bury "setturtle

to setturtlestate :ttl
  pu
  setpos first :ttl
  setheading first bf :ttl
  setpen last :ttl
end
bury "setturtlestate

;; creating and deleting turtles

to copyturtle
  ignore cloneturtle
end
bury "copyturtle

to cloneturtle
  localmake "oldturtle turtle
  saveturtlestate
  repeat 1000 [
    make ".curturtle :.curturtle + 1
    if :.curturtle > 1000 [make ".curturtle 1]
    if emptyp item turtle :.turtles [markturtle op :oldturtle]
  ]
  (throw "error [too many turtles])
end
bury "cloneturtle

to deleteturtle :ttl
  if :ttl = turtle [(throw "error [cannot delete current turtle])]
  .setitem :ttl :.turtles []
end
bury "deleteturtle

to resetturtles
  make ".turtles array 1000
  make ".curturtle 1
  markturtle
end
bury "resetturtles

;; nice shorthands

to spread :count
  repeat :count [copyturtle rt 360 / :count]
end
bury "spread

to allturtles
  op filter [not emptyp item ? :.turtles] iseq 1 1000
end
bury "allturtles

to alldo :.prog
  foreach allturtles [setturtle ? run :.prog]
end
bury "alldo