Select subexpression in equation

08012016, 11:04 AM
Post: #1




Select subexpression in equation
Hi,
Recently got an HP Prime and I love it, but there is one thing that drives me insane. It probably is just a lack of user knowledge but I cannot for the life of me figure out how to select/edit subexpressions in equations. I have to admit I have always been a 'sloppy' equation writer so I don't necessarily think too much about parentheses and ordering beforehand. On the previous HPs (previously owned 28S, 48SX, 49G and 50G  still use that last one) this didn't matter as I could always select a subexpression and edit it further. On the Prime however I cannot figure out how to do this. Example 1: I start writing x+1/y ... and then realise that I actually meant to write (x+1)/y, so have to go back add a () at the start, remove the ), add a () at the end, remove the (, etc. All a bit tedious. On the 50G this is easy, just press "up" key twice and then press "/" and all is good again. Example 2: I have this expression: (1+x+a)/(1+xa). I want to change it to (1+sqrt(x+a))/(1+sqrt(xa)). I cannot figure out how to do this other than reentering the equation from scratch. On the HP50G (&co) I could just select the subelements x+a and xa and apply the sqrt to these components. If anyone can tell me how to do this, I would be eternally grateful. Regards 

08012016, 01:22 PM
Post: #2




RE: Select subexpression in equation
Right now, there isn't a perfect solution, but you can go into Home settings and change the entry mode from textbook to algebraic, make the edits and switch back. Creating a user key to toggle between Entry:=1 and Entry:=0 can make this process much less tedious and keeps the text that's already on the entry line. It's also helpful to create two more user keys: one that returns "(" and another that returns ")". This makes inserting parentheses after the fact much easier.


08012016, 02:23 PM
(This post was last modified: 08012016 02:32 PM by Fortin.)
Post: #3




RE: Select subexpression in equation
The following assigns the textbook<>algebraic toggle code to the ShiftEEX (Sto>) key. The startview switches to the home settings (2) while the change is made so that the entry line is updated when returning to Home (1).
KEY KS_Eex() BEGIN STARTVIEW(−2,0); Entry:=IFTE(Entry==0,1,0); STARTVIEW(−1); RETURN ""; END; 

08022016, 04:05 AM
Post: #4




RE: Select subexpression in equation
Well that's disappointing ...
What I find frustrating is that it seems like the functionality is 'almost there', i.e. I can already click and drag to select subexpressions, but when I press a key like SQRT, the whole subexpression is then just replaced instead of edited. I am pretty sure it wouldn't be so hard to just take the selected piece and put it into the new expression (trivial for unary operators, but still could have a common sense default for things like fractions) But thanks a lot for the codesnippet! That helps, especially for my example 2. 

08022016, 02:02 PM
Post: #5




RE: Select subexpression in equation
(08022016 04:05 AM)Sanctuary Wrote: I can already click and drag to select subexpressions, but when I press a key like SQRT, the whole subexpression is then just replaced instead of edited. After selecting the text, press shiftview (copy), press the 'cut' softkey, insert the new token (sqrt for example), and then paste the cut text. If you choose to use the copy function's begin/end instead of click and drag method to select text, try to position the cursor before pressing shiftview (copy) and you'll save a begin or end press. I would like to see a 50Gstyle equation editor introduced to Prime  both for direct entry and for selecting partial text from history. A touch interface would be a very welcome addition. 

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