# Expression evaluator: rendering issue and feature confusion

Hello,

I am new to this universe of GA. I have been recently clicking around
bivector.net
in the tools tab of the page, I discovered that I can choose my GA, and it will display the multiplication table together with an expression evaluator.

Currently I am trying to understand 2D EPGA (Gunn variant - i.e. plane-based).
I am at the very beginning so I was just trying to do the operations in the cheat-sheet but manually.
After discovering the expression evaluator, even though I believed in my results, I fed it the following
expression:
(2e20 + 1e01 + 1e12) & (1e20 + 3e01 + 1e12)
where the & I think wants to be the join operator
(I am not 100% sure because I am not familiar with the ASCII based notation).

The output that I got out of it was not rendered correctly, as it can be seen in the below figure.

But the result itself according to my hand computations seems to be right, i.e. it seems that:
(2e20 + 1e01 + 1e12) & (1e20 + 3e01 + 1e12) = 5e0 - e2 - 2e1

I hope that this post brings attention to this problem and gets fixed because I would really like to be able to check my results while learning.

Also, I would like to propose adding the rest of the usable operators/functions into the list of the expression evaluator. Or even just a reference to some place that explains all the features built into this evaluator.

Hi Dominik,

I did some updates to the tools page, fixing those display issues and adding a bit more documentation on the supported operations.

Cheers,

S.

1 Like

Hi Steven,

thank you for the update, I already utilized it for checking the following example

\begin{aligned} R :=& e^{\frac{\pi}{4}e_{12}} \\ P :=& 1e_{20} + 1e_{12} \\ P_{new} :=& RP\tilde{R} \end{aligned}

as
( (E**(PI*e12/4)) >>> (1e20 + 1e12) ).Normalized
and everything rendered as expected.

This evaluator is a super tool, thanks again for polishing it even further .

Hi Dominik,

If you’re studying 3DPGA, you may appreciate another little writeup (with interactive graphs) I’m working on here : https://enki.ws/ganja.js/examples/coffeeshop.html#ydDtaGu0a&fullscreen

Cheers,

S.