Hiro Docs

Function Signature

(slice? sequence left-position right-position)

Input: sequence_A, uint, uint
Output: (optional sequence_A)

Why it matters

The slice? function is crucial for:

Extracting sub-sequences from sequences.
Implementing logic that requires partial data extraction.
Ensuring data integrity by validating indices for slicing.
Simplifying the process of handling sub-sequence extraction in smart contracts.

When to use it

Use slice? when you need to:

Extract a sub-sequence from a sequence.
Implement logic that requires partial data extraction.
Validate indices for slicing to ensure data integrity.
Handle sub-sequence extraction operations.

Best Practices

Ensure the left-position and right-position are within the bounds of the sequence.
Use meaningful variable names for better readability.
Combine with other sequence functions for comprehensive sequence management.
Handle the possible error cases to ensure robust contract behavior.

Practical Example: Extracting a Sub-sequence from a String

Let's implement a function that extracts a sub-sequence from a string:

(define-read-only (extract-substring (input (string-ascii 20)) (start uint) (end uint))
  (slice? input start end)
)

;; Usage
(extract-substring "blockstack" u5 u10) ;; Returns (some "stack")
(extract-substring "blockstack" u0 u5) ;; Returns (some "block")
(extract-substring "blockstack" u5 u15) ;; Returns none (out of bounds)

This example demonstrates:

Using slice? to extract a sub-sequence from a string.
Implementing a public function to handle the sub-sequence extraction.
Handling both successful and error cases.

Common Pitfalls

Using slice? with indices that are out of bounds, causing the operation to fail.
Assuming the sub-sequence will always be valid, leading to unhandled error cases.
Not handling all possible conditions, resulting in incomplete sequence management.
Overlooking the need for proper error handling and validation.

len: Returns the length of a sequence.
concat: Concatenates two sequences.
index-of?: Returns the first index at which an item can be found in a sequence.

The slice? function is a fundamental tool for extracting sub-sequences in Clarity smart contracts. It allows developers to implement logic that requires partial data extraction, ensuring data integrity and simplifying sequence handling. When used effectively, slice? enhances the reliability and maintainability of your smart contract code by providing a clear and concise way to handle sub-sequence extraction operations.

slice?