equal
deleted
inserted
replaced
1 def deriv (r: Rexp, c: Char) : Rexp = r match { |
1 def der (r: Rexp, c: Char) : Rexp = r match { |
2 case NULL => NULL |
2 case NULL => NULL |
3 case EMPTY => NULL |
3 case EMPTY => NULL |
4 case CHAR(d) => if (c == d) EMPTY else NULL |
4 case CHAR(d) => if (c == d) EMPTY else NULL |
5 case ALT(r1, r2) => ALT(deriv(r1, c), deriv(r2, c)) |
5 case ALT(r1, r2) => ALT(der(r1, c), der(r2, c)) |
6 case SEQ(r1, r2) => |
6 case SEQ(r1, r2) => |
7 if (nullable(r1)) ALT(SEQ(deriv(r1, c), r2), deriv(r2, c)) |
7 if (nullable(r1)) ALT(SEQ(der(r1, c), r2), der(r2, c)) |
8 else SEQ(deriv(r1, c), r2) |
8 else SEQ(der(r1, c), r2) |
9 case STAR(r) => SEQ(deriv(r, c), STAR(r)) |
9 case STAR(r) => SEQ(der(r, c), STAR(r)) |
10 } |
10 } |
11 |
11 |
|
12 def ders (s: List[Char], r: Rexp) : Rexp = s match { |
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13 case Nil => r |
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14 case c::s => ders(s, der(c, r)) |
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15 } |
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16 |