To review, context-free grammars (CFGs) are collections of templates that describe how to generate phrase types in terms of other phrase types.  To write that in Step, we have one task for each phrase type and one method for each rule/template.  Templates can fill in a sub-phrase by enclosing the sub-phrase's task in brackets:

Phrase: bla bla [Subphrase] bla

But what if you want the template to fill in text you specify yourself?  You can do that by adding a parameter (aka an argument¹) to your phrase/task.  Parameters are extra information you specify after the name of the task when you run it or write a method for it.  For example,

# Try: [Greet "Mr. Daniels"]
[randomly]
Greet ?who: Hello, ?who.
Greet ?who: Hey, ?who.
Greet ?who: Good morning, ?who.

This says that Greet needs an extra piece information: who is being greeted.  When you call Greet, you specify who should be greeted.  So instead of just typing [Greet] you’d type something like:

[Greet “Mr. Daniels”]

And this would generate one of the following:

• “Hello, Mr. Daniels.”
• “Hey, Mr. Daniels.”
• “Good Morning, Mr. Daniels.”

depending on which rule was chosen.

The quotation marks around “Mr. Daniels” are there so that if Greet takes more than one parameter, it can tell where the text of one parameter ends and another begins.  They’re not necessary if the text you specify is in lower case and doesn’t have any spaces in it.  So you can just say:

[Greet dawg]

Which is a little less typing than:

[Greet “dawg”]

But they both mean the same thing.² Both can generate text such as “Hey, dawg.”

Notes