DragginMath: Entering Expressions

Look at the top of the DragginMath screen. See a long text field there. Throughout DragginMath documentation, this text field is called Top Text. It is where you enter the equations you work on.

Whenever you tap Top Text, the screen is erased, and the screen keyboard rises up from the bottom. This is how you start working on your next problem. If you tap TopText by accident, you will lose your work, but in most cases, you can easily get it back.

If the screen keyboard is not visible, you cannot enter text into DragginMath, even if you have a hardware keyboard attached to your device.

A hardware keyboard is easier to use than the screen keyboard. But it doesn’t have all of the symbols needed to operate DragginMath, so you will use the screen keyboard for at least some of your interactions with the app.

Because of differences in screen size, the screen keyboards are different for iPad and iPhone. Each screen keyboard has its own Info page to help you understand it. These keyboards are designed for this purpose and easy to use, but there are some things you might not figure out if you haven’t read about them. Look for the Info ℹ️ icon in a lower corner of the keyboard. If you are left handed, there is a left-handed keyboard choice on the Configuration screen that can make life easier for you.

Let’s start with something basic: tap Top Text now and enter 2+3+4. As you type, notice things happening elsewhere on the screen. Some kind of picture is forming there. That picture is called an operator tree. Most of the work you do with DragginMath involves operator trees. This app exists to let you see and work with them. Later in this Guided Tour, we will talk about how they are made and why that is useful to know.

If you happen to enter something incorrect, such as 2++, the text field flashes red and your device (((beeps))). Notice that the incorrect character was not accepted. You may only enter expressions that are correct. Being correct doesn’t mean you have not made a mistake. In this context, a mistake is when you enter a character you didn’t intend, but it still follows the rules of math syntax, such as 2+6 when you wanted 2+3. If you make a mistake, use the ⬅️ key to back up. If you decide you want to simply start over, flick your fingertip sideways off the ⬅️ key to erase the whole line.

You may add or delete characters only at the end of Top Text. Cutting or pasting anywhere else is not allowed. The app reads and analyzes what you enter as you enter it, so it would become confused if you could type anywhere other than the end.

When you finish entering your expression, tap the ↵ key, which is like the return key on a hardware keyboard. This finishes the construction of the operator tree, which then moves to the middle of the screen.

If your expression has open parentheses that you haven’t closed, DragginMath quietly does that for you when you tap ↵. But if your expression is otherwise incomplete, the text field flashes red and your device (((beeps))). Remember that you may only enter expressions that are correct, which includes being complete.

If you have an incomplete expression and you decide you are no longer interested in it, flick your finger sideways off the ⬅️ key. Just as before, this erases the whole line. You may then tap the ↵ key with an empty text field, and the screen keyboard politely goes away. If you still have an incomplete expression lying around, it won’t.

The 🔠 key shifts to uppercase.

The Assign ≕ key provides an operator that associates an expression with a name. For example, if you enter x↑2+y↑2≕P, tapping P replaces itself with x↑2+y↑2. Names can only be single uppercase letters. Tapping the ≕ key automatically shifts to uppercase.