Previous row reference

[SGarno]

One thing I would like to suggest is the ability to enter in operators which automatically reference the previous row.

For example, if you enter:

R1 : 100 * 40

then, on R2 you enter

R2: + 200

It should assume that the addition is to the previous row. This would allow streamlined entry, such as:

R1: 500 + 20
R2: * 20%
R3: + ( 300 / 50 )
R4: * 1.07

This also allows a formula to be adjusted without having to update references. Meaning you can move things around (i.e. add a new line and not have to update the formulas. For example, you wanted to add more to R3 but in a separate line. You could just insert a new row

R1: 500 + 20
R2: + 100
R3: * 20%
R4: + ( 300 / 50 )
R5: * 1.07

Now, R3 is taking 20% of 620 instead of just 520, but you didn't have to update any formulas. Just add a new line and operator with value.

Sweet!

[kazad]

Great feedback. I've wondered whether/how to auto-reference rows without interfering too much with regular math, something like:

-200
+300
-400
sum(r1:r3)

[as a tally]. However, I think your use case is more common. (One philosophy I like is 'Make the easy things easy, and the hard things possible.').

I think auto-referencing the previous row is the right move (there is ANS + 10), I'll think about this more, and whether there's a good way to say "No, really, i just want positive 200 as an item".

[SGarno]

It should only work on operators. anything that is A {something} B. For functions, you would have to do the operator first (which makes sense anyway). So your example, would become:

-200
+300
-400
/ sum(r1:r3)

Which would then divide the results by the sum of r1:r3

[kazad]

Interesting. I like the / sum(r1:r3), it reads well. I realize Excel may have solved this for me: if you do just want +200 (as a value, not operating on previous row) then you can write =+200 (Instacalc supports leading =, since many users write that since they come from Excel). I'll have to think about edge cases a bit more...

[kazad]

Ok, thought about it. Essentially, all operators make sense as "autoreference previous row" except for unary - for negation:

• -20 is negative 20
• - 20 is subtract 20 from previous row

It's a subtle difference, but most likely what people mean (will have a message in the row info area). For now, this will be for the main "calculator arithmetic" operators (+ - * / ^) and not the "fancy programming operators" (& or not < > etc.). Once you're doing "programming" (not tallying) you know enough to keep things on the same line. (This may be something to revisit.)

Having the logic be "movable" is an interesting side effect.

[kazad]

Ok, a preview for this is live:

https://instacalc.com/59763

Tally example

-200           = -200
+300           = 100
-400           = -400
/ sum(r1:r3)   = 0.8

Going to let it marinate for a bit and see if any errors come up. Great suggestion, thanks for the feedback.

[SGarno]

Yeah that looks great!

And being able to drag around the rows and (essentially) manipulate the formula without really updating the formula is very slick. I was playing with an exchange rate formula that caculates the fees on exchanging to another currency, The bottom number is the effective loss and the top three numbers are the different amounts I was playing with. What was awesome was I could just drag the different amounts to exchange and it would update the rest of the calculations automagically. Quick and easy to go between values and not lose values for previous calcs.

An interesting side effect (which actually is not an problem....but it is a curiosity):

You can't get to the value in the row, only the result. Because the notation is now so concise, it almost appears like you could get the value. For example, initially in a new row, I entered R4 thinking I was going to get the exchange rate (5.02) but ended up with the converted currency; which is correct, but it caught me a bit off guartd at first. I want to play with named variables a bit more and see what I can accomplish with this tally approach and row movements.

Very slick! Great job on this!

[kazad]

Ah, nice scenario! Didn't think about the "drag to try new parameters" but that's a great side effect.

Yeah, row references have always been the raw output: it does make me think about something like r4.input or something, as a way to pull out numbers used inside the row.

The closest may be something like

rate = 5.02
change = .38

As a named param, then you can have things like

/ rate

Rate - change

To use them. (There is a bit of trickiness with adding percentages; 100 + 10% works, if you do x = 10% then later 100 + x, it will be "100 + .1", so you'd do "100 * (1 + x)" in a formula.)