tasks a-s

Task/Set/Go/set.go

@@ -0,0 +1,124 @@
+package main
+
+import "fmt"
+
+type set map[int]bool
+
+func main() {
+    // task: set creation
+    s0 := make(set)             // create empty set
+    s1 := set{3: true}          // create set with one element
+    s2 := set{3: true, 1: true} // create set with two elements
+
+    // option: another way to create a set
+    s3 := newSet([]int{3, 1, 4, 1, 5, 9})
+
+    // option: output!
+    fmt.Println("s0:", s0)
+    fmt.Println("s1:", s1)
+    fmt.Println("s2:", s2)
+    fmt.Println("s3:", s3)
+
+    // task: element predicate
+    fmt.Printf("%v ∈ s0: %t\n", 3, s0.hasElement(3))
+    fmt.Printf("%v ∈ s3: %t\n", 3, s3.hasElement(3))
+    fmt.Printf("%v ∈ s3: %t\n", 2, s3.hasElement(2))
+
+    // task: union
+    b := set{4: true, 2: true}
+    fmt.Printf("s3 ∪ %v: %v\n", b, union(s3, b))
+
+    // task: intersection
+    fmt.Printf("s3 ∩ %v: %v\n", b, intersection(s3, b))
+
+    // task: difference
+    fmt.Printf("s3 \\ %v: %v\n", b, difference(s3, b))
+
+    // task: subset predicate
+    fmt.Printf("%v ⊆ s3: %t\n", b, subset(b, s3))
+    fmt.Printf("%v ⊆ s3: %t\n", s2, subset(s2, s3))
+    fmt.Printf("%v ⊆ s3: %t\n", s0, subset(s0, s3))
+
+    // task: equality
+    s2Same := set{1: true, 3: true}
+    fmt.Printf("%v = s2: %t\n", s2Same, equal(s2Same, s2))
+
+    // option: proper subset
+    fmt.Printf("%v ⊂ s2: %t\n", s2Same, properSubset(s2Same, s2))
+    fmt.Printf("%v ⊂ s3: %t\n", s2Same, properSubset(s2Same, s3))
+
+    // option: delete.  it's built in.
+    delete(s3, 3)
+    fmt.Println("s3, 3 deleted:", s3)
+}
+
+func newSet(ms []int) set {
+    s := make(set)
+    for _, m := range ms {
+        s[m] = true
+    }
+    return s
+}
+
+func (s set) String() string {
+    if len(s) == 0 {
+        return "∅"
+    }
+    r := "{"
+    for e := range s {
+        r = fmt.Sprintf("%s%v, ", r, e)
+    }
+    return r[:len(r)-2] + "}"
+}
+
+func (s set) hasElement(m int) bool {
+    return s[m]
+}
+
+func union(a, b set) set {
+    s := make(set)
+    for e := range a {
+        s[e] = true
+    }
+    for e := range b {
+        s[e] = true
+    }
+    return s
+}
+
+func intersection(a, b set) set {
+    s := make(set)
+    for e := range a {
+        if b[e] {
+            s[e] = true
+        }
+    }
+    return s
+}
+
+func difference(a, b set) set {
+    s := make(set)
+    for e := range a {
+        if !b[e] {
+            s[e] = true
+        }
+    }
+    return s
+}
+
+func subset(a, b set) bool {
+    for e := range a {
+        if !b[e] {
+            return false
+        }
+    }
+    return true
+}
+
+func equal(a, b set) bool {
+    return len(a) == len(b) && subset(a, b)
+}
+
+func properSubset(a, b set) bool {
+    return len(a) < len(b) && subset(a, b)
+}