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300
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     1  | 
import CW9c._
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153
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     2  | 
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221
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assert(der('a', ZERO | ONE) == (ZERO | ZERO))
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assert(der('a', (CHAR('a') | ONE) ~ CHAR('a')) == ALT((ONE | ZERO) ~ CHAR('a'), ONE))
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300
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     5  | 
assert(der('a', (CHAR('a') | CHAR('a')) ~ CHAR('a')) == (ONE | ONE) ~ CHAR('a'))
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221
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     6  | 
assert(der('a', STAR(CHAR('a'))) == (ONE ~ STAR(CHAR('a'))))
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assert(der('b', STAR(CHAR('a'))) == (ZERO ~ STAR(CHAR('a'))))
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300
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     9  | 
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    10  | 
val r0_urban = "a" ~ "b" ~ "c"
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    11  | 
assert(der('a', r0_urban) == (ONE ~ "b") ~ "c")
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    12  | 
assert(der('b', r0_urban) == (ZERO ~ "b") ~ "c")
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    13  | 
assert(der('c', r0_urban) == (ZERO ~ "b") ~ "c")
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    14  | 
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    15  | 
val r1_urban = (ONE ~ "b") ~ "c"
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    16  | 
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    17  | 
assert(der('a', r1_urban) == ((ZERO ~ "b") | ZERO) ~ "c")
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    18  | 
assert(der('b', r1_urban) == ((ZERO ~ "b") | ONE) ~ "c")
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    19  | 
assert(der('c', r1_urban) == ((ZERO ~ "b") | ZERO) ~ "c")
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    20  | 
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    21  | 
val r2_urban = ((ZERO ~ "b") | ONE) ~ "c"
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    22  | 
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    23  | 
assert(der('a', r2_urban) == ((((ZERO ~ "b") | ZERO) ~ "c") | ZERO))
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    24  | 
assert(der('b', r2_urban) == ((((ZERO ~ "b") | ZERO) ~ "c") | ZERO))
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    25  | 
assert(der('c', r2_urban) == ((((ZERO ~ "b") | ZERO) ~ "c") | ONE))
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