Merge pull request JuliaLang#30 from SaschaMann/smann/ex-custom-set

Add exercise: custom set

config.json

@@ -178,6 +178,19 @@
         "filtering",
         "mathematics"
       ]
+    },
+    {
+      "slug": "custom-set",
+      "difficulty": 5,
+      "topics": [
+        "types",
+        "parametric types",
+        "methods",
+        "multiple dispatch",
+        "function extension",
+        "mathematics",
+        "iterators"
+      ]
     }
   ],
   "deprecated": [

exercises/custom-set/HINTS.md

@@ -0,0 +1 @@
+The tests require a constructor that takes an array. The internals of your custom set implementation can use other data structures but you may have to implement an outer constructor that takes exactly one array for the tests to pass.

exercises/custom-set/example.jl

@@ -0,0 +1,51 @@
+import Base: AbstractSet, isempty, length, in, issubset, start, next, done,
+             push!, ==, copy, intersect!, intersect, union!, union
+
+type CustomSet{T} <: AbstractSet
+    elements::Array{T, 1}
+end
+
+isempty(s::CustomSet) = isempty(s.elements)
+length(s::CustomSet) = length(s.elements)
+in(element, s::CustomSet) = in(element, s.elements)  # this also defines issubset(::CustomSet, ::CustomSet)
+==(s1::CustomSet, s2::CustomSet) = issubset(s1, s2) && issubset(s2, s1)
+copy(s::CustomSet) = CustomSet(copy(s.elements))
+push!(s::CustomSet, element) = push!(s.elements, element)
+
+# Iterator protocol
+start(::CustomSet) = 1
+next(s::CustomSet, state) = s.elements[state], state + 1
+done(s::CustomSet, state) = state > length(s)
+
+function disjoint(s1::CustomSet, s2::CustomSet)
+    for element in s1
+        element in s2 && return false
+    end
+    return true
+end
+
+function complement!(s1::CustomSet, s2::CustomSet)
+    for (i, element) in enumerate(s1)
+        element in s2 && deleteat!(s1.elements, i)
+    end
+    return s1
+end
+complement(s1::CustomSet, s2::CustomSet) = complement!(copy(s1), s2)
+
+function intersect!(s1::CustomSet, s2::CustomSet)
+    tbd = Int[]
+    for (i, element) in enumerate(s1)
+        element in s2 || push!(tbd, i)
+    end
+    deleteat!(s1.elements, tbd)
+    return s1
+end
+intersect(s1::CustomSet, s2::CustomSet) = intersect!(copy(s1), s2)
+
+function union!(s1::CustomSet, s2::CustomSet)
+    for element in s2
+        element in s1 || push!(s1, element)
+    end
+    return s1
+end
+union(s1::CustomSet, s2::CustomSet) = union!(copy(s1), s2)

exercises/custom-set/runtests.jl

@@ -0,0 +1,200 @@
+using Base.Test
+
+include("custom-set.jl")
+
+# canonical data
+@testset "empty" begin
+    @test  isempty(CustomSet([]))
+    @test !isempty(CustomSet([1]))
+end
+
+@testset "in (contains)" begin
+    @test !(1 in CustomSet([]))
+    @test   1 in CustomSet([1, 2, 3])
+    @test !(4 in CustomSet([1, 2, 3]))
+end
+
+@testset "subset" begin  # TODO ⊆, ⊈
+    @test  issubset(CustomSet([]), CustomSet([]))
+    @test  issubset(CustomSet([]), CustomSet([1]))
+    @test !issubset(CustomSet([1]), CustomSet([]))
+    @test  issubset(CustomSet([1, 2, 3]), CustomSet([1, 2, 3]))
+    @test  issubset(CustomSet([1, 2, 3]), CustomSet([4, 1, 2, 3]))
+    @test !issubset(CustomSet([1, 2, 3]), CustomSet([4, 1, 3]))
+end
+
+@testset "disjoint" begin
+    @test  disjoint(CustomSet([]), CustomSet([]))
+    @test  disjoint(CustomSet([]), CustomSet([1]))
+    @test  disjoint(CustomSet([1]), CustomSet([]))
+    @test !disjoint(CustomSet([1, 2]), CustomSet([2, 3]))
+    @test  disjoint(CustomSet([1, 2]), CustomSet([3, 4]))
+end
+
+@testset "equal" begin
+    @test CustomSet([]) == CustomSet([])
+    @test CustomSet([]) != CustomSet([1, 2, 3])
+    @test CustomSet([1, 2, 3]) != CustomSet([])
+    @test CustomSet([1, 2]) == CustomSet([2, 1])
+    @test CustomSet([1, 2, 3]) != CustomSet([1, 2, 4])
+end
+
+@testset "add" begin
+    @test begin
+        custom_set = CustomSet([])
+        push!(custom_set, 3)
+        custom_set == CustomSet([3])
+    end
+    @test begin
+        custom_set = CustomSet([1, 2, 4])
+        push!(custom_set, 3)
+        custom_set == CustomSet([1, 2, 3, 4])
+    end
+    @test begin
+        custom_set = CustomSet([1, 2, 3])
+        push!(custom_set, 3)
+        custom_set == CustomSet([1, 2, 3])
+    end
+end
+
+@testset "intersection" begin
+    @testset "in-place" begin
+        @test begin
+            cs1 = CustomSet([])
+            cs2 = CustomSet([])
+            intersect!(cs1, cs2)
+            isempty(cs1)
+        end
+        @test begin
+            cs1 = CustomSet([])
+            cs2 = CustomSet([3, 2, 5])
+            intersect!(cs1, cs2)
+            isempty(cs1)
+        end
+        @test begin
+            cs1 = CustomSet([1, 2, 3, 4])
+            cs2 = CustomSet([])
+            intersect!(cs1, cs2)
+            isempty(cs1)
+        end
+        @test begin
+            cs1 = CustomSet([1, 2, 3])
+            cs2 = CustomSet([4, 5, 6])
+            intersect!(cs1, cs2)
+            isempty(cs1)
+        end
+        @test begin
+            cs1 = CustomSet([1, 2, 3, 4])
+            cs2 = CustomSet([3, 2, 5])
+            intersect!(cs1, cs2)
+            cs1 == CustomSet([2, 3])
+        end
+    end
+    @testset "not in-place" begin  # TODO use operator ∩
+        @test isempty(intersect(CustomSet([]), CustomSet([])))
+        @test isempty(intersect(CustomSet([]), CustomSet([3, 2, 5])))
+        @test isempty(intersect(CustomSet([1, 2, 3, 4]), CustomSet([])))
+        @test isempty(intersect(CustomSet([1, 2, 3]), CustomSet([4, 5, 6])))
+        @test intersect(CustomSet([1, 2, 3, 4]), CustomSet([3, 2, 5])) == CustomSet([2, 3])
+    end
+end
+
+@testset "complement (difference)" begin
+    @testset "in-place" begin
+        @test begin
+            cs1 = CustomSet([])
+            cs2 = CustomSet([])
+            complement!(cs1, cs2)
+            isempty(cs1)
+        end
+        @test begin
+            cs1 = CustomSet([])
+            cs2 = CustomSet([3, 2, 5])
+            complement!(cs1, cs2)
+            isempty(cs1)
+        end
+        @test begin
+            cs1 = CustomSet([1, 2, 3, 4])
+            cs2 = CustomSet([])
+            complement!(cs1, cs2)
+            cs1 == CustomSet([1, 2, 3, 4])
+        end
+        @test begin
+            cs1 = CustomSet([3, 2, 1])
+            cs2 = CustomSet([2, 4])
+            complement!(cs1, cs2)
+            cs1 == CustomSet([1, 3])
+        end
+    end
+    @testset "not in-place" begin
+        @test isempty(complement(CustomSet([]), CustomSet([])))
+        @test isempty(complement(CustomSet([]), CustomSet([3, 2, 5])))
+        @test complement(CustomSet([1, 2, 3, 4]), CustomSet([])) == CustomSet([1, 2, 3, 4])
+        @test complement(CustomSet([3, 2, 1]), CustomSet([2, 4])) == CustomSet([1, 3])
+    end
+end
+
+@testset "union" begin
+    @testset "in-place" begin
+        @test begin
+            cs1 = CustomSet([])
+            cs2 = CustomSet([])
+            union!(cs1, cs2)
+            isempty(cs1)
+        end
+        @test begin
+            cs1 = CustomSet([])
+            cs2 = CustomSet([2])
+            union!(cs1, cs2)
+            cs1 == CustomSet([2])
+        end
+        @test begin
+            cs1 = CustomSet([1, 3])
+            cs2 = CustomSet([])
+            union!(cs1, cs2)
+            cs1 == CustomSet([1, 3])
+        end
+        @test begin
+            cs1 = CustomSet([1, 3])
+            cs2 = CustomSet([2, 3])
+            union!(cs1, cs2)
+            cs1 == CustomSet([3, 2, 1])
+        end
+    end
+    @testset "not in-place" begin
+        @test isempty(union(CustomSet([]), CustomSet([])))
+        @test union(CustomSet([]), CustomSet([2])) == CustomSet([2])
+        @test union(CustomSet([1, 3]), CustomSet([])) == CustomSet([1, 3])
+        @test union(CustomSet([1, 3]), CustomSet([2, 3])) == CustomSet([3, 2, 1])
+    end
+end
+
+# language specific tests
+@testset "implements correct abstract type" begin
+    @test CustomSet <: Base.AbstractSet
+end
+
+@testset "length" begin
+    @test length(CustomSet([])) == 0
+    @test length(CustomSet([1, 2, 3])) == 3
+end
+
+@testset "iterable" begin
+    @test begin
+        cs1 = CustomSet([1, 2, 3, 4])
+        cs2 = CustomSet([])
+        for element in cs1
+            push!(cs2, element)
+        end
+        cs1 == cs2
+    end
+end
+
+@testset "copy" begin
+    @test begin
+        cs1 = CustomSet([1, 2, 3])
+        cs2 = copy(cs1)
+        push!(cs1, 4)
+        cs2 == CustomSet([1, 2, 3])
+    end
+end