return (X[0]**2 - X[1]**2, 2*X[0]*X[1])

import ampl, sys

class AMPLToPythonConverter:
  def __init__(self, stream):
    self.stream = stream

  def visit_reference(self, expr):
    self.stream.write(expr.name)

  def visit_binary(self, expr):
    expr.lhs.accept(self)
    self.stream.write(' {} '.format(expr.op))
    expr.rhs.accept(self)

  def visit_decl(self, decl):
    if decl.kind == 'minimize':
      self.stream.write("def {}(x):n".format(decl.name))
      self.stream.write("  return ");
      decl.body.accept(self)
      self.stream.write('n')

compound_stmt = ampl.parse(
  """
  var x;
  minimize f: x * x;
  """, "input")

for node in compound_stmt.nodes:
  node.accept(AMPLToPythonConverter(sys.stdout))

def f(x):
  return x * x