Here's another exercise like that at the end of the tutorial. The idea is to see what really counts as a grammatically correct sentence of SL...and what doesn't. So, it's good to play around with these a bit.
Here's the idea of a grammatially correct sentence:
Atomic Sentences: Any upper case letter (e.g., 'A', 'L') standing alone as a sentence or an upper case letter followed by a name (lower case from 'a' to 'u'); so 'Ma' is also an example.
Molecular Sentences: Take the atomic sentences plus connectives ('&', '>', '~', 'v', '=') and build up to give things like '(A&L)' or '~(A&L)' or '(~(A&L)&Ma)'. You can even write: '~~(A&L)' buit by adding the tilda twice!
And you can drop outside parentheses when you are finished building. So, '~(A&L)&Ma' is also OK.
Each of the following expressions breaks the rules of correct grammar. Change the expression slightly (e.g., add a connective or parrentheses) to make it fit the rules for sentence construction. Then press TAB. If an exclamation point is added, you're new expression is gramatically correct! If you get "???" added, then go back and do it again!