Hiro Docs

Using the bit-not function for bitwise complement operations in Clarity smart contracts.

Function Signature

(bit-not i1)

Input: An integer (int or uint)
Output: An integer of the same type as the input (int or uint)

Why it matters

The bit-not function is crucial for:

Performing bitwise complement operations in smart contracts.
Implementing certain logical operations and algorithms.
Manipulating binary data at the bit level.
Creating bitmasks for various purposes.

When to use it

Use the bit-not function when you need to:

Invert all bits in an integer value.
Create a bitmask for bitwise operations.
Implement certain cryptographic or hashing algorithms.
Perform low-level data manipulations.

Best Practices

Be aware of the differences between signed (int) and unsigned (uint) integers when using bit-not.
Remember that bit-not on a uint will result in a large positive number due to two's complement representation.
Use bit-not in combination with other bitwise operations (bit-and, bit-or, bit-xor) for complex bit manipulations.
Consider the readability of your code when using bitwise operations extensively.

Practical Example: Simple Flag System

Let's implement a simple flag system using bit-not and other bitwise operations:

(define-constant FLAG_A u1)  ;; 0001
(define-constant FLAG_B u2)  ;; 0010
(define-constant FLAG_C u4)  ;; 0100
(define-constant FLAG_D u8)  ;; 1000

(define-data-var user-flags uint u0)

(define-public (toggle-flag (flag uint))
  (ok (var-set user-flags (bit-xor (var-get user-flags) flag))))

(define-public (clear-all-flags-except (flag uint))
  (ok (var-set user-flags (bit-and (var-get user-flags) flag))))

(define-public (set-all-flags-except (flag uint))
  (ok (var-set user-flags (bit-and (bit-not (var-get user-flags)) flag))))

(define-read-only (has-flag (flag uint))
  (is-eq flag (bit-and (var-get user-flags) flag)))

This example demonstrates:

Using bit-not in combination with bit-and to set all flags except a specific one.
Implementing a flag system using bitwise operations for efficient storage and manipulation.
Combining bit-not with other bitwise operations for complex flag manipulations.

Common Pitfalls

Forgetting that bit-not on a uint results in a large positive number, not a negative number.
Overlooking the sign bit when using bit-not with signed integers.
Not considering the full range of bits when applying bit-not to smaller integer values.

bit-and: Used for bitwise AND operations.
bit-or: Used for bitwise OR operations.
bit-xor: Used for bitwise XOR operations.
bit-shift-left: Used for left-shifting bits.
bit-shift-right: Used for right-shifting bits.

The bit-not function is a powerful tool for bitwise operations in Clarity smart contracts. When used in combination with other bitwise functions, it enables efficient implementation of flags, bitmasks, and low-level data manipulations. However, developers should be mindful of the differences between signed and unsigned integers and the potential for unexpected results when not used carefully.

bit-not