1 // Preliminary Part about Code Similarity

     2 //========================================

     3 

     4 

     5 object CW7a { 

     6 

     7 //(1) Complete the clean function below. It should find

     8 //    all words in a string using the regular expression

     9 //    \w+  and the library function 

    10 //

    11 //         some_regex.findAllIn(some_string)

    12 //

    13 //    The words should be Returned as a list of strings.

    14 

    15 def clean(s: String) : List[String] = 

    16   ("""\w+""".r).findAllIn(s).toList

    17 

    18 

    19 //(2) The function occurrences calculates the number of times  

    20 //    strings occur in a list of strings. These occurrences should 

    21 //    be calculated as a Map from strings to integers.

    22 

    23 def occurrences(xs: List[String]): Map[String, Int] =

    24   (for (x <- xs.distinct) yield (x, xs.count(_ == x))).toMap

    25 

    26 //(3) This functions calculates the dot-product of two documents

    27 //    (list of strings). For this it calculates the occurrence

    28 //    maps from (2) and then multiplies the corresponding occurrences. 

    29 //    If a string does not occur in a document, the product is zero.

    30 //    The function finally sums up all products. 

    31 

    32 def prod(lst1: List[String], lst2: List[String]) : Int = {

    33     val words = (lst1 ::: lst2).distinct

    34     val occs1 = occurrences(lst1)

    35     val occs2 = occurrences(lst2)

    36     words.map{ w => occs1.getOrElse(w, 0) * occs2.getOrElse(w, 0) }.sum

    37 }

    38 

    39 //(4) Complete the functions overlap and similarity. The overlap of

    40 //    two documents is calculated by the formula given in the assignment

    41 //    description. The similarity of two strings is given by the overlap

    42 //    of the cleaned (see (1)) strings.  

    43 

    44 def overlap(lst1: List[String], lst2: List[String]) : Double = {

    45     val m1 = prod(lst1, lst1)

    46     val m2 = prod(lst2, lst2) 

    47     prod(lst1, lst2).toDouble / (List(m1, m2).max)

    48 }

    49 

    50 def similarity(s1: String, s2: String) : Double =

    51   overlap(clean(s1), clean(s2))

    52 

    53 

    54 /*

    55 

    56 

    57 val list1 = List("a", "b", "b", "c", "d") 

    58 val list2 = List("d", "b", "d", "b", "d")

    59 

    60 occurrences(List("a", "b", "b", "c", "d"))   // Map(a -> 1, b -> 2, c -> 1, d -> 1)

    61 occurrences(List("d", "b", "d", "b", "d"))   // Map(d -> 3, b -> 2)

    62 

    63 prod(list1,list2) // 7 

    64 

    65 overlap(list1, list2)   // 0.5384615384615384

    66 overlap(list2, list1)   // 0.5384615384615384

    67 overlap(list1, list1)   // 1.0

    68 overlap(list2, list2)   // 1.0

    69 

    70 // Plagiarism examples from 

    71 // https://desales.libguides.com/avoidingplagiarism/examples

    72 

    73 val orig1 = """There is a strong market demand for eco-tourism in

    74 Australia. Its rich and diverse natural heritage ensures Australia's

    75 capacity to attract international ecotourists and gives Australia a

    76 comparative advantage in the highly competitive tourism industry."""

    77 

    78 val plag1 = """There is a high market demand for eco-tourism in

    79 Australia. Australia has a comparative advantage in the highly

    80 competitive tourism industry due to its rich and varied natural

    81 heritage which ensures Australia's capacity to attract international

    82 ecotourists."""

    83 

    84 similarity(orig1, plag1)

    85 

    86 

    87 // Plagiarism examples from 

    88 // https://www.utc.edu/library/help/tutorials/plagiarism/examples-of-plagiarism.php

    89 

    90 val orig2 = """No oil spill is entirely benign. Depending on timing and

    91 location, even a relatively minor spill can cause significant harm to

    92 individual organisms and entire populations. Oil spills can cause

    93 impacts over a range of time scales, from days to years, or even

    94 decades for certain spills. Impacts are typically divided into acute

    95 (short-term) and chronic (long-term) effects. Both types are part of a

    96 complicated and often controversial equation that is addressed after

    97 an oil spill: ecosystem recovery."""

    98 

    99 val plag2 = """There is no such thing as a "good" oil spill. If the

   100 time and place are just right, even a small oil spill can cause damage

   101 to sensitive ecosystems. Further, spills can cause harm days, months,

   102 years, or even decades after they occur. Because of this, spills are

   103 usually broken into short-term (acute) and long-term (chronic)

   104 effects. Both of these types of harm must be addressed in ecosystem

   105 recovery: a controversial tactic that is often implemented immediately

   106 following an oil spill."""

   107 

   108 overlap(clean(orig2), clean(plag2))

   109 similarity(orig2, plag2)

   110 

   111 // The punchline: everything above 0.6 looks suspicious and 

   112 // should be looked at by staff.

   113 

   114 */

   115 

   116 

   117 }