Task: Set
C: #include <stdio.h>

typedef unsigned int set_t; 

void show_set(set_t x, const char *name)
{
	int i;
	printf("%s is:", name);
	for (i = 0; (1U << i) <= x; i++)
		if (x & (1U << i))
			printf(" %d", i);
	putchar('\n');
}

int main(void)
{
	int i;
	set_t a, b, c;
	
	a = 0; 
	for (i = 0; i < 10; i += 3) 
		a |= (1U << i);
	show_set(a, "a");

	for (i = 0; i < 5; i++)
		printf("\t%d%s in set a\n", i, (a & (1U << i)) ? "":" not");

	b = a;
	b |= (1U << 5); b |= (1U << 10); 
	b &= ~(1U << 0);	
	show_set(b, "b");

	show_set(a | b, "union(a, b)");
	show_set(c = a & b, "c = common(a, b)");
	show_set(a & ~b, "a - b"); 
	show_set(b & ~a, "b - a");
	printf("b is%s a subset of a\n", !(b & ~a) ? "" : " not");
	printf("c is%s a subset of a\n", !(c & ~a) ? "" : " not");

	printf("union(a, b) - common(a, b) %s union(a - b, b - a)\n",
		((a | b) & ~(a & b)) == ((a & ~b) | (b & ~a))
			? "equals" : "does not equal");

	return 0;
}

Go: package main

import "fmt"








type set map[complex128]bool

func main() {
    
    s0 := make(set)             
    s1 := set{3: true}          
    s2 := set{3: true, 1: true} 

    
    s3 := newSet(3, 1, 4, 1, 5, 9)

    
    fmt.Println("s0:", s0)
    fmt.Println("s1:", s1)
    fmt.Println("s2:", s2)
    fmt.Println("s3:", s3)

    
    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))

    
    b := set{4: true, 2: true}
    fmt.Printf("s3 ∪ %v: %v\n", b, union(s3, b))

    
    fmt.Printf("s3 ∩ %v: %v\n", b, intersection(s3, b))

    
    fmt.Printf("s3 \\ %v: %v\n", b, difference(s3, b))

    
    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))

    
    s2Same := set{1: true, 3: true}
    fmt.Printf("%v = s2: %t\n", s2Same, equal(s2Same, s2))

    
    fmt.Printf("%v ⊂ s2: %t\n", s2Same, properSubset(s2Same, s2))
    fmt.Printf("%v ⊂ s3: %t\n", s2Same, properSubset(s2Same, s3))

    
    delete(s3, 3)
    fmt.Println("s3, 3 deleted:", s3)
}

func newSet(ms ...complex128) 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 complex128) 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)
}