Logical operators

The logical operators work on Boolean values. Actually, every value serves as a Boolean value. When used with logical operators, every value behaves either like true or like false. The values 0, () and {} are all treated as false by the logical operators (in fact, {} = false). All other values are treated as true. Some logical operators leverage this property by returning the first value that determines the outcome.

(When trying out the examples below, remember that false is equal to {}, which is also how it prints out.)

@> true && true@> true && false@> 1 && () && 0@> 1 && 0 && ()@> false || false@> false || 0 || {1: 2}@> false || true@> 0 || 42@> 0 || (x: 1) || ()@> !(x: 1)@> !{}@> !!{1, 2, 3}

Bitwise operators? Nope!

Arr.ai omits bitwise operators by design. Many other languages use integers to encode bitwise information. Such integers are often called bitmasks. Logically speaking, a uint64 in Go may be thought of as a set of numbers, n, in the range 0 ≤ n < 64. For a given uint64, it can be said that the set contains the number n if bit n is set to one. For example, the number 75 has the bit pattern 01001011. Since only bits 0, 1, 3 and 6 are set to 1, the number 75 represents the set {0, 1, 3, 6}.

That last point offers a pretty strong hint as to why arr.ai doesn't support bitwise operators. Put simply, they are not needed. Arr.ai can work directly with sets of integers without having to fake it using bitmasks. In fact, it supports sets with integers of any size, including negative numbers, as well as fractions, infinity, and you can even mix in some non-integers if your problem demands it.

@> /set a = {1, 2, 3, 4}@> /set b = {3, 4, 5, 6}@> /set c = {5, 6, 7, 8}@> [a & b, b & c, a & c]     # intersection@> [a | b, b | c, a | c]     # union@> [a &~ b, b &~ c, a &~ c]  # difference (aka AND-NOT)@> [a ~~ b, b ~~ c, a ~~ c]  # symmetric difference (aka XOR)@> {1, 2, 0.5, //math.pi^0.5, "duck"}  # Mix it up!

In real world languages, especially those with no built-in concept of sets, numeric bitmasks are often used to represent integer sets. To support interoperability, arr.ai provides the //bits package to convert between integer sets and their numeric representations.

@> //bits.set(42)@> //bits.mask({1, 3, 5})@> //bits.mask({-1, -3})