Alerts might not be the most pleasant form of interaction with a Scheem
program, but they can be helpful when debugging. Let's implement
alert, making sure to implement it as a pre-defined
function value rather than a special form.
For Node.js, have the implementation log a value to the console for debugging. On the web do a real alert.
Test your function with:
Add a function
value. Note that
(alert expr) evaluates
expr before showing the alert.