Thanks for the nice summary!

A minor problem with the overall approach proposed is that the result is semantically not correct. For example, one cannot take the resulting _expression_ and use it, as is, in a computer-algebra-system session within texmacs (which can be done with "properly written" expressions). I am unaware of how to achieve the typesetting you described, preserving the semantics. Of course, for the sake of typesetting only this does not matter. 

Peter.

On 13 Sep 2018, at 22:35, Jorge Fernández de Cossío Díaz <address@hidden> wrote:

Phantom seems to be the solution. To summarize the answers scattered in this thread:

1. Parenthesize each line independently.
2. In the first line remove the closing parenthesis and in the second line remove the opening parenthesis.
3. If there is a large operator in one line missing from the other line the brackets size will not match. Copy/paste the operator to the line that doesn't have it, select it and do Format -> Special -> Phantom to hide it. This will make the bracket of matching size.

Thank you all!

On Thu, Sep 13, 2018 at 4:20 PM Kostas Oikonomou <address@hidden> wrote:

You can try Format -> Special -> Phantom  (seems to work like in Latex).

On 09/13/2018 16:15, Peter Rapčan wrote:

As Basile said, you can increase the size of the parentheses using Focus > Increase Size (while inside the group). I tried it now and, unfortunately, it seems to work only before deleting one of the brackets of the opening-closing bracket pair, which is inconvenient but of course circumventable by adding a fresh bracket pair every time the bracket on the other line changes size.

I hope Joris can step in and tell us the proper way to do this… :-)

Peter.

On 13 Sep 2018, at 22:01, Jorge Fernández de Cossío Díaz <address@hidden> wrote:

If one of the lines has a big symbol (like an integral) and the other doesn't, then the brackets will be of different sizes. In Lyx one solves this by inserting an "invisible" symbol of matching size in the other line, that doesn't show up in the rendered document but that takes care of resizing the brackets. Is there something similar in TeXmacs?

On Thu, Sep 13, 2018 at 3:52 PM Peter Rapčan <address@hidden> wrote:

I “solve” this by putting braces in both lines and deleting the closing brace on the first line and the opening brace on the last line (there have to be some symbols inside the brackets otherwise you cannot erase just a single side of the bracket pair as far as I remember).

I would welcome a better and more correct way to achieve what you describe, but I am unaware of one.

Cheers,
Peter.

> On 13 Sep 2018, at 20:02, Jorge Fernández de Cossío Díaz <address@hidden> wrote:
>
> I have a long equation that spans multiple lines and has parentheses. Here is an example (I wrote this in lyx):
>
> <image.png>
>
> I know how to write equations in multiple lines in TeXmacs. But notice the outer braces in this example. They span multiple lines and have matching sizes. Is it possible to get this effect in TeXmacs? How?
>