A user has reported that iOS 7 exposes a bug in J (at least I assume it is a bug in J rather than iOS, but there is a tiny chance some future iOS update will fix the problem).
The problem is the keyboard is disabled in 'stacked input state'. E.g., if you type sentence f=: 3 : 0 and then keyboard return, J is in a state that accepts input lines until the closing right paren, but for some reason the keyboard is disabled so you are stuck. There are 2 workarounds: Using the J return button (immediately to the right of the input area) instead of the keyboard return button (for an unknown reason) keeps the keyboard enabled when entering stacked input state. This allows you to enter sentences for the definition and then provide the closing right paren. Curiously this colors the return button blue and subsequent inputs color it the expected green. Second workaround is to avoid stacked input state and instead enter the definition in a temporary ijs file in the E window. This involves a few extra steps but in general can be more efficient as you can easily edit the definition. If stuck with the keyboard disabled you can kill the J task, but a cleaner recovery is to get the closing right paren entered another way. If you have a closing right paren on a line in the session you can recall it to the input line and enter it with the green return. Or you can switch to Notes app, enter and copy a right paren and then switch back to J and paste it and press the green return. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
