1 // Core Part 2 about Code Similarity

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

     3 

     4 

     5 object C2 { 

     6 

     7 

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

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

    10 //    \w+  and the library function 

    11 //

    12 //         some_regex.findAllIn(some_string)

    13 //

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

    15 

    16 

    17 def clean(s: String) : List[String] = ???

    18   

    19 

    20 

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

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

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

    24 

    25 

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

    27 

    28 

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

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

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

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

    33 //    The function finally sums up all products. 

    34 

    35 

    36 def prod(lst1: List[String], lst2: List[String]) : Int = ???

    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 strings (see (1)).  

    43 

    44 

    45 def overlap(lst1: List[String], lst2: List[String]) : Double = ???

    46 

    47 def similarity(s1: String, s2: String) : Double = ???

    48 

    49 

    50 

    51 /* Test cases

    52 

    53 

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

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

    56 

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

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

    59 

    60 prod(list1,list2) // 7 

    61 

    62 overlap(list1, list2)   // 0.5384615384615384

    63 overlap(list2, list1)   // 0.5384615384615384

    64 overlap(list1, list1)   // 1.0

    65 overlap(list2, list2)   // 1.0

    66 

    67 // Plagiarism examples from 

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

    69 

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

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

    72 capacity to attract international ecotourists and gives Australia a

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

    74 

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

    76 Australia. Australia has a comparative advantage in the highly

    77 competitive tourism industry due to its rich and varied natural

    78 heritage which ensures Australia's capacity to attract international

    79 ecotourists."""

    80 

    81 similarity(orig1, plag1) // 0.8679245283018868

    82 

    83 

    84 // Plagiarism examples from 

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

    86 

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

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

    89 individual organisms and entire populations. Oil spills can cause

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

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

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

    93 complicated and often controversial equation that is addressed after

    94 an oil spill: ecosystem recovery."""

    95 

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

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

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

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

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

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

   102 recovery: a controversial tactic that is often implemented immediately

   103 following an oil spill."""

   104 

   105 overlap(clean(orig2), clean(plag2))  // 0.728

   106 similarity(orig2, plag2)             // 0.728

   107 

   108 

   109  

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

   111 // should be investigated by staff.

   112 

   113 */

   114 

   115 }