# TiKz dash dash plus plus

Unfortunately due to the way search engines work, this information isn't that easy to find.

Sometimes examples draw using `--`, sometimes `-- +`, sometimes `-- ++`.

I don't get the meaning!

For example, for this command:

``````\draw[fill=gray!50] (1,1) -- + (0:.5) arc (0:60:1) -- cycle;
``````

What is the `-- +` there?

What does it mean if I change that to `--` ?

• I've added a reference to the manual for further reading. – Andrew Stacey Aug 6 '12 at 19:14
• Which is here – bobobobo Aug 9 '12 at 16:26

The pluses modify the following coordinate making it relative to the previous saved coordinate. The difference between a single and a double plus is whether or not the saved coordinate is updated.

Thus:

``````\draw (1,1) -- ++(1,0) -- ++(0,1);
``````

the second coordinate is actually `(1,1) + (1,0) = (2,1)` and the third is `(2,1) + (0,1) = (2,2)`.

``````\draw (1,1) -- +(1,0) -- ++(0,1);
``````

the second coordinate is actually `(1,1) + (1,0) = (2,1)` but the second coordinate is not saved so the third is relative to the first and thus is `(1,1) + (0,1) = (1,2)`.

There's a slight change for bezier curves. If you do `\draw (1,1) .. controls +(1,0) and +(0,1) .. ++(2,2)` then the second control point is computed relative to the end point (which is very useful) and thus the controls are `(1,1) + (1,0)` for the first and `(2,2) + (1,1) + (0,1)` for the second (as the end point is itself relative to the initial position since the control points were specified with a single plus).

(Forgot to add the reference to the manual: to learn more, see Section 13.4 in the PGF manual (PGF2.10 version, might be a different section in other versions))