Hello World

Let's write your first Keel program!

Using the REPL

The easiest way to try Keel is using the REPL (Read-Eval-Print Loop):

keel repl

Once in the REPL, type:

"Hello, World!"

You should see:

"Hello, World!"

Your First Function

Let's define a function that greets someone by name:

fn greet : String -> String
fn greet name = "Hello, " ++ name ++ "!"

greet "World"

This outputs:

"Hello, World!"

Breaking It Down

1. fn greet : String -> String - This declares a function named greet that takes a String and returns a String
2. fn greet name = ... - This defines the function body, where name is the parameter
3. ++ - This is the string concatenation operator

Next Steps

• Learn more about the basics of Keel
• Explore functions in depth
• Try the playground to experiment online