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Even More Advanced Syntax Highlighting
======================================

Syntax highlighting in Vim is a topic that could easily fill a book of its own.

We're going to cover one last important part of it here and then move on to
other things.  If you want to learn more you can read the Vim documentation with
`:help syntax` and look at syntax files other people have made.

Highlighting Strings
--------------------

Potion, like most programming languages, supports string literals like `"Hello,
world!"`.  We should highlight these as strings.  To do this we'll use the
`syntax region` command.  Add the following to your Potion syntax file:

    :::vim
    syntax region potionString start=/\v"/ skip=/\v\\./ end=/\v"/
    highlight link potionString String

Close and reopen your `factorial.pn` file and you'll see that the string at the
end of the file is highlighted!

The last line here should be familiar.  Reread the previous two chapters if you
don't understand what it does.

The first line adds to a syntax group using a "region".  Regions have a "start"
pattern and an "end" pattern that specify where they start and end.  In this
case, a Potion string starts when we see a double quote and ends when we see the
next double quote.

The "skip" argument to `syntax region` allows us to handle string escapes like
`"She said: \"Vimscript is tricky, but useful\"!"`.

If we didn't use the `skip` argument Vim would end the string at the `"` before
`Vimscript`, which is not what we want!

In a nutshell, the `skip` argument to `syntax region` tells Vim: "once you start
matching this region, I want you to ignore anything that matches `skip`, even if
it would normally be considered the end of the region".

Take a few minutes and think through this.  What happens with something like
`"foo \\" bar"`?  Is that the correct behavior?  Will that *always* be the
correct behavior?  Close this book, take a few minutes and really *think* about
this!

Exercises
---------

Add syntax highlighting for single quoted strings.

Read `:help syn-region`.

Reading that should take longer than reading this chapter.  Pour yourself
a drink, you've earned it!