This changes the calling convention for calling a Javascript function from Python so that any proxied arguments are automatically destroyed at the end of the function call. This is a breaking change. It should make it much more convenient to use the foreign function interface. 

The docs need to be updated to explain the new calling convention before this can be merged. We should put a link to the appropriate section in the docs into the error message emitted when a borrowed proxy is used after it is free so that people have an easy time learning the model by trial and error.
ENH Destroy proxies created in JsProxy.__call__ when done with call. This changes the calling convention for calling a Javascript function from Python so that any proxied arguments are automatically destroyed at the end of the function call. This is a breaking change. It should make it much more convenient to use the foreign function interface. 

The docs need to be updated to explain the new calling convention before this can be merged. We should put a link to the appropriate section in the docs into the error message emitted when a borrowed proxy is used after it is free so that people have an easy time learning the model by trial and error.
# from: http://continuum.io/blog/numba_performance
# setup: N = 10 ; import numpy as np ; image = np.random.rand(N, N, 3) ; state = np.zeros((N, N, 2)) ; state_next = np.empty_like(state) ; state[0, 0, 0] = state[0, 0, 1] = 1   # noqa
# run: growcut(image, state, state_next, 2)

# pythran export growcut(float[][][], float[][][], float[][][], int)
import math


def window_floor(idx, radius):
    if radius > idx:
        return 0
    else:
        return idx - radius


def window_ceil(idx, ceil, radius):
    if idx + radius > ceil:
        return ceil
    else:
        return idx + radius


def growcut(image, state, state_next, window_radius):
    changes = 0
    sqrt_3 = math.sqrt(3.0)

    height = image.shape[0]
    width = image.shape[1]

    for j in range(width):
        for i in range(height):

            winning_colony = state[i, j, 0]
            defense_strength = state[i, j, 1]

            for jj in range(
                window_floor(j, window_radius), window_ceil(j + 1, width, window_radius)
            ):
                for ii in range(
                    window_floor(i, window_radius),
                    window_ceil(i + 1, height, window_radius),
                ):
                    if ii != i and jj != j:
                        d = image[i, j, 0] - image[ii, jj, 0]
                        s = d * d
                        for k in range(1, 3):
                            d = image[i, j, k] - image[ii, jj, k]
                            s += d * d
                        gval = 1.0 - math.sqrt(s) / sqrt_3

                        attack_strength = gval * state[ii, jj, 1]

                        if attack_strength > defense_strength:
                            defense_strength = attack_strength
                            winning_colony = state[ii, jj, 0]
                            changes += 1

            state_next[i, j, 0] = winning_colony
            state_next[i, j, 1] = defense_strength

    return changes

# from: http://continuum.io/blog/numba_performance
# setup: N = 10 ; import numpy as np ; image = np.random.rand(N, N, 3) ; state = np.zeros((N, N, 2)) ; state_next = np.empty_like(state) ; state[0, 0, 0] = state[0, 0, 1] = 1   # noqa
# run: growcut(image, state, state_next, 2)

# pythran export growcut(float[][][], float[][][], float[][][], int)
import math


def window_floor(idx, radius):
    if radius > idx:
        return 0
    else:
        return idx - radius


def window_ceil(idx, ceil, radius):
    if idx + radius > ceil:
        return ceil
    else:
        return idx + radius


def growcut(image, state, state_next, window_radius):
    changes = 0
    sqrt_3 = math.sqrt(3.0)

    height = image.shape[0]
    width = image.shape[1]

    for j in range(width):
        for i in range(height):

            winning_colony = state[i, j, 0]
            defense_strength = state[i, j, 1]

            for jj in range(
                window_floor(j, window_radius), window_ceil(j + 1, width, window_radius)
            ):
                for ii in range(
                    window_floor(i, window_radius),
                    window_ceil(i + 1, height, window_radius),
                ):
                    if ii != i and jj != j:
                        d = image[i, j, 0] - image[ii, jj, 0]
                        s = d * d
                        for k in range(1, 3):
                            d = image[i, j, k] - image[ii, jj, k]
                            s += d * d
                        gval = 1.0 - math.sqrt(s) / sqrt_3

                        attack_strength = gval * state[ii, jj, 1]

                        if attack_strength > defense_strength:
                            defense_strength = attack_strength
                            winning_colony = state[ii, jj, 0]
                            changes += 1

            state_next[i, j, 0] = winning_colony
            state_next[i, j, 1] = defense_strength

    return changes
