Bitwise Operations

Bitwise operations work on the individual bits of an integer value. They are the foundation of bit masks, packed flags, binary protocols, and other low-level numeric code. Unlike the logical operators, they evaluate both operands and combine them bit by bit rather than as truth values.

Operators

let a: uint8 = 0b00001100; // 12
let b: uint8 = 0b00001010; // 10

let and = a & b;  // 0b00001000 = 8   — bits set in both
let or  = a | b;  // 0b00001110 = 14  — bits set in either
let xor = a ^ b;  // 0b00000110 = 6   — bits set in exactly one
let not = ~a;     // 0b11110011 = 243 — every bit inverted

&, |, and ^ are binary; ~ is unary. The result has the type of the operand(s).

Operand Types

Both operands of a binary bitwise operation must have the same type; mixed-width or signed/unsigned combinations require an explicit as cast first:

let wide: uint32 = 0xFF;
let mask: uint8  = 0x0F;

let invalid = wide & mask;             // error: different operand types
let valid = wide & (mask as uint32);   // OK

Unsigned integers are the natural home for bit manipulation, since their bits carry no sign. bool also supports &, |, ^, and ~ as non-short-circuiting alternatives to the logical operators.

Common Patterns

Combining a bitwise operator with a shifted mask gives the four standard single-bit operations:

var flags: uint32 = 0;

flags |= 1 << 3;                      // set bit 3
flags &= ~(1 << 3);                   // clear bit 3
flags ^= 1 << 2;                      // toggle bit 2
let isSet = (flags & (1 << 2)) != 0;  // test bit 2

Parenthesise the shift that builds the mask so the grouping is unmistakable.

Compound Assignment

&, |, and ^ have compound assignment forms that update a mutable left operand in place:

var perms: uint8 = 0;
perms |= 0b100;   // grant
perms &= ~0b100;  // revoke

Bitwise vs. Logical

Bitwise & and | are easy to confuse with logical && and ||:

• Bitwise (&, |, ^, ~) combine the bits of integer values and always evaluate both operands.
• Logical (&&, ||, !) combine bool truth values and short-circuit.

Use logical operators for conditions and bitwise operators for masks and flags.

Precedence

Unary ~ binds tightest of all operators. Among the binary bitwise operators, AND is tighter than XOR, which is tighter than OR — and all three sit above the comparison and logical operators, but below shifts and arithmetic:

~  >  &  >  ^  >  |  >  comparisons  >  &&  >  ||

Because & outranks ==, the test flags & mask != 0 already groups as (flags & mask) != 0 — though parentheses make it clearer:

let isSet = (flags & mask) != 0;

See Operator Precedence for the complete precedence table.

See Also

• Shift Operations — << and >>, used to build masks
• Logical Operations — &&, ||, ! for conditions
• Unsigned Integer Types — per-type bit behaviour