| 374 | | def __init__(self, band=None, v=None): |
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| 375 | | super(BalanceConstraint, self).__init__(band[0], band[1], v) |
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| 376 | | self.band = band |
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| 377 | | b1, b2 = self.band |
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| 378 | | w = b2 - b1 |
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| 379 | | if w != 0: |
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| 380 | | self.balance = (v - b1) / w |
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| 381 | | else: |
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| 382 | | self.balance = 0 |
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| 383 | | self.v = v |
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| 384 | | print 'b', self.balance |
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| 385 | | |
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| 386 | | def solve_for(self, var): |
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| 387 | | b1, b2 = self.band |
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| 388 | | w = b2 - b1 |
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| 389 | | var.value = b1 + w * self.balance |
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| 390 | | |
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| 391 | | |
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| 392 | | |
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| 393 | | class BalanceConstraint(Constraint): |
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| 394 | | """ |
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| 395 | | Ensure that a variable @v is between values specified by @band |
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| 396 | | and in distance proportional from @band[0]. |
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| 397 | | |
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| 398 | | Consider |
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| 399 | | >>> from solver import Variable, WEAK |
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| 400 | | >>> a, b, c = Variable(2.0), Variable(3.0), Variable(2.3, WEAK) |
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| 401 | | >>> bc = BalanceConstraint(band=(a,b), v=c) |
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| 402 | | >>> c.value = 2.4 |
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| 403 | | >>> c |
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| 404 | | Variable(2.4, 10) |
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| 405 | | >>> bc.solve_for(c) |
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| 406 | | >>> a, b, c |
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| 407 | | (Variable(2, 20), Variable(3, 20), Variable(2.3, 10)) |
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| 408 | | |
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| 409 | | Band does not have to be band[0] < band[1] |
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| 410 | | >>> a, b, c = Variable(3.0), Variable(2.0), Variable(2.45, WEAK) |
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| 411 | | >>> bc = BalanceConstraint(band=(a,b), v=c) |
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| 412 | | >>> c.value = 2.50 |
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| 413 | | >>> c |
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| 414 | | Variable(2.5, 10) |
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| 415 | | >>> bc.solve_for(c) |
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| 416 | | >>> a, b, c |
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| 417 | | (Variable(3, 20), Variable(2, 20), Variable(2.45, 10)) |
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| 418 | | """ |
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| 419 | | |
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