Pure sequencing ties

[Jzellner]

I'm having trouble with ties in chapter 7. In particular, drill 6 states that 'D is not taller than C,' which is represented as a tie. I don't understand why. The rule does not forbid C from being taller than D. Why does the solution treat it as if it does?

[Adam Tyson]

Hey there JZ, thanks for asking, because the diagramming tool that we use for that type of rule (the one that looks like a long, stretched out equals sign) can easily be confused for something that it is not. It is NOT intended to be an equals sign, indicating that a tie is required. Rather, that symbol means "before or the same time as" - either they are tied or, as you surmised, C is before D.

The book does say that C can only tie for last (shortest), and what we mean by that is that C cannot be shortest by itself. Perhaps we should have said that instead? C need not be shortest, because he can be taller than D, but he also can be shortest IF he is tied with D.

Sorry for the confusion there! Good catch! From now on, whenever you see that funky looking elongated equals sign, just remember that it means "before or tied with", and not just "tied with".