345449.vhj5l3oj7.asia: StrategyPattern.py

Wed Dec 26 16:00:00 GMT 2001

StrategyPattern

#: c06:StrategyPattern.py

# The strategy interface:
class FindMinima:
  # Line is a sequence of points:
  def algorithm(self, line) : pass

# The various strategies:
class LeastSquares(FindMinima):
  def algorithm(self, line):
    return [ 1.1, 2.2 ] # Dummy

class NewtonsMethod(FindMinima):
  def algorithm(self, line):
    return [ 3.3, 4.4 ]  # Dummy

class Bisection(FindMinima):
  def algorithm(self, line):
    return [ 5.5, 6.6 ] # Dummy

class ConjugateGradient(FindMinima):
  def algorithm(self, line):
    return [ 3.3, 4.4 ] # Dummy

# The "Context" controls the strategy:
class MinimaSolver:
  def __init__(self, strategy):
    self.strategy = strategy

def minima(self, line):
    return self.strategy.algorithm(line)

def changeAlgorithm(self, newAlgorithm):
    self.strategy = newAlgorithm

solver = MinimaSolver(LeastSquares())
line = [
    1.0, 2.0, 1.0, 2.0, -1.0, 3.0, 4.0, 5.0, 4.0 
  ]
print solver.minima(line)
solver.changeAlgorithm(Bisection())
print solver.minima(line)
#:~

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