Unison Debugging: Tips and Tricks

Have you ever written a piece of code that just refuses to work, no matter what you do? Well, fear not my friend, for you are not alone. Debugging is an art form, and like any art form, it requires practice, patience, and perseverance. That's why today, we're going to talk about Unison Debugging: Tips and Tricks.

What is Unison?

Before we dive into the specifics of Unison Debugging, let's take a moment to talk about Unison itself. For those of you who don't know, Unison is a modern, functional programming language designed for building distributed systems. It's type-safe, built on a strong foundation of lambda calculus, and has first-class support for version control. In short, it's awesome.

Why Debugging is Important

Debugging is the process of finding and fixing errors in code. It's an essential part of the development process, and no matter how good a programmer you are, you're going to need to debug your code at some point. Debugging allows you to:

• Catch errors before they make it to production
• Improve the reliability of your code
• Speed up development by catching bugs early
• Learn from your mistakes and become a better programmer

Debugging in Unison

Now that we know what Unison is and why debugging is important, let's talk about Unison Debugging: Tips and Tricks. Unison has a lot of great built-in tools for debugging, and we're going to cover some of the best ones below.

1. Use the debug Function

The debug function is a built-in function in Unison that allows you to print out the value of a variable at runtime. It's incredibly useful for debugging, as it allows you to see exactly what's happening with your code as it's running.

For example, let's say you have a function that's supposed to add two numbers together, but for some reason, it's not working. You could use the debug function to see what's happening at runtime:

add x y =
  debug x
  debug y
  x + y

This would print out the values of x and y every time the function is called, allowing you to see exactly what's going on.

2. Use the print Function

The print function is another built-in function in Unison that's great for debugging. It allows you to print out a string at runtime, which can be incredibly useful for debugging complex code.

For example, let's say you have a function that's supposed to sort a list of integers, but for some reason, it's not working. You could use the print function to see what's happening at runtime:

sort list =
  print "Sorting list..."
  list.sortedBy (\x -> x)

This would print out the string "Sorting list..." every time the function is called, allowing you to see exactly what's happening.

3. Use the assert Function

The assert function is a built-in function in Unison that allows you to check if a condition is true at runtime. If the condition is not true, the function will throw an error.

For example, let's say you have a function that's supposed to divide two numbers, but for some reason, it's not working. You could use the assert function to make sure that the second number is not 0:

divide x y =
  assert (y != 0) "Cannot divide by 0!"
  x / y

This would throw an error if the second number is 0, allowing you to catch the error early and fix it.

4. Use the Unison REPL

The Unison REPL (Read-Eval-Print-Loop) is a powerful tool for debugging Unison code. It allows you to interactively execute code and test out different scenarios, making it ideal for debugging.

To get started with the Unison REPL, simply open up your terminal and type unison repl. This will launch the REPL, allowing you to start running code.

5. Use the trace Function

The trace function is a built-in function in Unison that allows you to print out a message at runtime, along with the value of a variable. It's incredibly useful for debugging complex code, as it allows you to see exactly what's happening with your code as it's running.

For example, let's say you have a function that's supposed to calculate the factorial of a number, but for some reason, it's not working. You could use the trace function to see what's happening at runtime:

factorial n =
  if n == 0 then
    1
  else
    let result = factorial (n - 1)
    trace ("Factorial of " ++ (show n) ++ " is " ++ (show (result * n))) (result * n)

This would print out a message every time the function is called, showing you the value of n, as well as the calculated factorial.

Conclusion

Debugging is an essential part of the development process, and Unison has a lot of great built-in tools for debugging. By using the tips and tricks outlined above, you can speed up your development process, catch bugs early, and become a better programmer. So go forth and debug!

Additional Resources