Just came across codetogo for ipad.  It has been around a while, but there didnt seem to be a mention of it previously.  You can write dlang code with syntax highlighting, and run it if you have an Internet connection.  I don't know yet how it works with multi file programs, imports, etc, but a nice tool to have when you travel.

https://itunes.apple.com/us/app/codetogo/id382677229?mt=8

Stuck on a plane now thanks to the wrong kind of snow.