print

Function Signature

(print expr)

• Input: A
• Output: A

Why it matters

The print function is crucial for:

1. Debugging and logging expressions during contract development.
2. Evaluating and returning the input expression.
3. Enhancing code readability and maintainability by providing a way to output intermediate values.

When to use it

Use print when you need to:

• Debug and log expressions during contract development.
• Evaluate and return an input expression.
• Output intermediate values for better understanding of contract behavior.

Best Practices

• Use print primarily for debugging and development purposes.
• Ensure that the expression passed to print is meaningful and necessary for debugging.
• Remove or comment out print statements in production code to avoid unnecessary output.

Practical Example: Printing an Expression

Let's implement a function that prints the result of an addition operation:

(define-read-only (add-and-print (a int) (b int))
  (print (+ a b))
)

;; Usage
(add-and-print 3 4) ;; Prints 7 and returns 7
(add-and-print 10 20) ;; Prints 30 and returns 30

This example demonstrates:

1. Using print to output the result of an addition operation.
2. Implementing a public function to handle the addition and printing.
3. Handling both small and large input values.

Common Pitfalls

1. Using print excessively, leading to cluttered output and reduced readability.
2. Assuming print is necessary for all expressions, leading to overuse.
3. Not removing or commenting out print statements in production code, resulting in unnecessary output.

Related Functions

• +: Adds two or more numbers.
• -: Subtracts one number from another.
• *: Multiplies two or more numbers.
• /: Divides one number by another.

Conclusion

The print function is a fundamental tool for debugging and logging expressions in Clarity smart contracts. It allows developers to evaluate and return input expressions, providing a way to output intermediate values for better understanding of contract behavior. When used effectively, print enhances the reliability and maintainability of your smart contract code by providing a clear and concise way to debug and log expressions.