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1 signature SCANNER_SEQ = |
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2 sig |
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3 type 'a seq |
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4 |
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5 val pull : 'a seq -> ('a * 'a seq) option |
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6 end |
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7 |
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8 signature EXTENDED_SCANNER_SEQ = |
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9 sig |
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10 |
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11 include SCANNER_SEQ |
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12 |
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13 val null : 'a seq -> bool |
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14 val length : 'a seq -> int |
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15 val take_at_most : 'a seq -> int -> 'a list |
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16 |
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17 end |
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18 |
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19 functor ExtendScannerSeq (structure Seq : SCANNER_SEQ) : EXTENDED_SCANNER_SEQ = |
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20 struct |
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21 |
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22 type 'a seq = 'a Seq.seq |
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23 |
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24 val pull = Seq.pull |
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25 |
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26 fun null s = is_none (pull s) |
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27 |
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28 fun take_at_most s n = |
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29 if n <= 0 then [] else |
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30 case pull s of |
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31 NONE => [] |
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32 | SOME (x,s') => x::(take_at_most s' (n-1)) |
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33 |
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34 fun length' s n = |
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35 case pull s of |
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36 NONE => n |
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37 | SOME (_, s') => length' s' (n+1) |
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38 |
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39 fun length s = length' s 0 |
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40 |
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41 end |
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42 |
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43 signature VECTOR_SCANNER_SEQ = |
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44 sig |
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45 include EXTENDED_SCANNER_SEQ |
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46 |
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47 val fromString : string -> string seq |
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48 val fromVector : 'a Vector.vector -> 'a seq |
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49 end |
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50 |
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51 structure VectorScannerSeq :> VECTOR_SCANNER_SEQ = |
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52 struct |
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53 |
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54 structure Incubator : SCANNER_SEQ = |
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55 struct |
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56 |
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57 type 'a seq = 'a Vector.vector * int * int |
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58 fun pull (v, len, i) = if i >= len then NONE else SOME (Vector.sub (v, i), (v, len, i+1)) |
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59 |
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60 end |
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61 |
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62 structure Extended = ExtendScannerSeq (structure Seq = Incubator) |
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63 |
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64 open Extended |
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65 |
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66 fun fromVector v = (v, Vector.length v, 0) |
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67 fun vector_from_string s = Vector.tabulate (String.size s, fn i => String.str (String.sub (s, i))) |
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68 fun fromString s = fromVector (vector_from_string s) |
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69 |
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70 end |
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71 |
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72 signature LIST_SCANNER_SEQ = |
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73 sig |
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74 include EXTENDED_SCANNER_SEQ |
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75 |
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76 val fromString : string -> string seq |
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77 val fromList : 'a list -> 'a seq |
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78 end |
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79 |
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80 structure ListScannerSeq :> LIST_SCANNER_SEQ = |
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81 struct |
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82 |
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83 structure Incubator : SCANNER_SEQ = |
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84 struct |
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85 |
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86 type 'a seq = 'a list |
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87 fun pull [] = NONE |
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88 | pull (x::xs) = SOME (x, xs) |
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89 |
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90 end |
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91 |
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92 structure Extended = ExtendScannerSeq (structure Seq = Incubator) |
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93 |
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94 open Extended |
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95 |
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96 val fromList = I |
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97 val fromString = Symbol.explode |
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98 |
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99 end |