import numpy as np
import grid


class smberror(Exception):
  def __init__(self, val):
    self.value = val
  def __str__(self):
    return repr(self.value)

def rms(errors):
  """
    root mean square calculation
  """
  r = 0.0
  for i in errors:
    r += np.power(i, 2)
  r = np.sqrt(r / len(errors))
  return r

def exact_func(x, y):
  return np.power((np.sin(x * np.pi) * np.cos(y * np.pi)), 2)
  return np.sin(x * np.pi) * np.cos(y * np.pi)


def get_mesh(source, destination, use_structured_grid = False):
  mesh_source = None
  mesh_dest   = None
  if use_structured_grid:
    mesh_source = grid.simple_rect_grid(source, source)
    mesh_dest   = grid.simple_rect_grid(destination, destination)
  else:
    mesh_source = grid.simple_random_grid(source)
    mesh_dest   = grid.simple_random_grid(destination)

  if not (mesh_dest and mesh_source):
    raise smberror('problem creating mesh objects')
  else:
    return mesh_source, mesh_dest