"""
OST Skunkworks: Freakish Tractor
generator that moves forward to a boundary reading
current character, writing current marker. Fuel
might run out. send protocol may be employed to
tank up, redirect, change the marker. Farm is an
n x m array, presumably smallish, for interactive
console experiments.
-- Python track, O'Reilly School of Technology
Also:
"""
class Farm:
def __init__(self, rows=8, columns=8, facing="N", bg="*"):
self.h = rows
self.w = columns
self.facing = facing
self.bg = bg # background character
self.tractors = [] # like Snake or Dog stomach
self.field = [list(bg*self.w) for x in range(self.h)] # model
self.framenumber = 0
self.trace = []
def add(self, tractor):
self.tractors.append(tractor)
def ticktock(self): # controller
"""tick tock o' the clock
time marches on!
Advance each tractor in the direction it's facing,
ignoring stuck tractors already at a fence (some
types of Tractor are smarter than others about fences).
"""
for tractor in self.tractors:
try:
next(tractor) # state changer
except StopIteration:
pass # harmless stuck tractor signal
self.framenumber += 1
return self.framenumber
def render(self):
display=""
for line in self.field:
display += "".join(line)+"\n"
return display # view
__str__ = render
def __repr__(self):
return "Farm({},{}) @ {}".format(self.w, self.h, id(self))
def tractor(thefarm , pos = [0,0], facing="N", marker="O", fuel=10):
"pos is mutable = current position"
while True:
y,x = pos
if fuel > 0:
if facing == "N":
if y > 0:
y -= 1
else:
raise StopIteration
elif facing == "S":
if y < thefarm.h - 1:
y += 1
else:
raise StopIteration
elif facing == "W":
if x > 0:
x -= 1
else:
raise StopIteration
elif facing == "E":
if x < thefarm.w - 1:
x += 1
else:
raise StopIteration
fuel -= 1
pos = (y,x)
else:
raise StopIteration
changes = yield (thefarm.field[y][x], pos, fuel)
thefarm.field[y][x] = marker
if changes:
facing = changes.get('facing',facing)
marker = changes.get('marker',marker)
fuel = changes.get('fuel',fuel)
pos = changes.get('pos',pos)
def _test(n):
# Agile Programming: TDD is your friend
thefarm = Farm(20,20, bg = ".")
print("Empty field, all is peaceful", thefarm, sep="\n\n") # frame of film
t1 = tractor(thefarm, pos=[10,10], marker="O", facing="N")
t2 = tractor(thefarm, pos=[10,11], marker="X", facing="S")
thefarm.add(t1)
thefarm.add(t2)
print("Showing the tractors in a list: ", thefarm.tractors, "===", sep="\n")
print("A busy day begins...", thefarm, sep="\n\n") # frame of film
for arrow_of_time in range(n):
thefarm.ticktock() # much physics involved in terms of what's a realistic throughput
print("After {} ticks of the clock, the tractors have moved...".format(n),
thefarm, sep="\n\n") # frame of film
if __name__ == "__main__":
_test(10)
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