What a great moment we stand upon regarding iOS text editors now that Editorial is on the iPhone. You can pick how much customization you need in your text editor between Editorial, 1Writer and others. If you're fond to numbers in your essays, the simple built-in calculator in Editorial may grow on you, however, Calca just authenticated its x-callback-url support and becomes a perfect match for 1Writer.
We already covered replace selection actions in 1Writer here. Remember that with a few changes these workflows also apply for Editorial.
Calca has 2 URL schemes, The simplest,
create, is to create a new document and supports the
body parameter. The one we're aiming at is
calc since it grabs a
body and allows you to return the result in the x-success using the
Select any equation in your piece and trigger the action. It will bounce to Calca and return to 1Writer. Magically, your equation was replaced by its result. Since Calca is a full-blown calculator, you can do more complex math as well, such as matrices, trigonometry, logarithms and others. For the whole spec, check their reference documentation.
If you're still in doubt if your writing workflow demands the Editorial level of expertise, then you should probably give another shot at 1Writer. As you can see, it has a ton of tricks available as well.