| 472 |      1 | 
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|  |      2 | 
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|  |      3 | def urbanmain() = {
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|  |      4 |   import M3._
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| 221 |      5 | 
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| 472 |      6 |   assert(nullable(ZERO) == false)
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|  |      7 |   assert(nullable(ONE) == true)
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|  |      8 |   assert(nullable(CHAR('a')) == false)
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|  |      9 |   assert(nullable(ZERO | ONE) == true)
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|  |     10 |   assert(nullable(ZERO | CHAR('a')) == false)
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|  |     11 |   assert(nullable(ONE ~  ONE) == true)
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|  |     12 |   assert(nullable(ONE ~ CHAR('a')) == false)
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|  |     13 |   assert(nullable(STAR(ZERO)) == true)
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|  |     14 |   assert(nullable(ALTs(List(ONE, CHAR('a'), ZERO))) == true)
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|  |     15 |   assert(nullable(SEQs(List(ONE, ALTs(List(ONE, CHAR('a'), ZERO)), STAR(ZERO)))) == true)
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|  |     16 | }
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