[Tex/LaTex] Is it ever bad to use \left and \right

bracketsmath-mode

For mathematics, is it ever disadvantageous to use \left( and \right) in equations?

I can't see any way that doing this would hinder the typesetting, so why isn't () just converted into \left( \right) automatically? This would save a lot of typing.

Cheers!

Best Answer

The automatic sized braces are not always the sizes you would choose manually, but that's a matter of personal taste (and the sizes chosen by the automatic algorithm can be adjusted with the \delimitershortfall and \delimiterfactor parameters).

More immediate problems are that \left( ... \right) differs from ( ... ) even if the standard small delimiter size is chosen.

It is a \mathinner atom so it gets additional spacing in many contexts.
It is a \mathinner atom so can not be broken across lines in a math display such as align.
It is a \mathinner atom so will not allow automatic linebreaking in inline math.
It is a \mathinner atom so forms a box set to its natural length and white space around relations or added explicitly will not be allowed to stretch or shrink to help with line breaking.
It is a \mathinner atom.

Related Solutions

[Tex/LaTex] Inserting evil red code in LyX in mathmode

[Something of an extended comment]

Lyx can handle a variety of math mode items, but where it cannot handle them you have to insert raw LaTeX code ('ERT'). Other than extending the Lyx binary, there is not much that can be done here. (Even then, there will still be limits to what Lyx can handle.)

[Tex/LaTex] How to implement an ‘&’ inside a \left( \right) environment

A simplified version of your code:

\begin{align}
x = y \left(5 + 3 & + 1\right. 
\end{align}

I strongly suspect that the problem is caused by the ampersand being inside the \left( ... \right. [construct]. ... Is there any way to get this to work?

Your suspicion is correct. A short answer to your question: "No." Medium-length answer: "No way." Long answer: "Hell No."

Why? A \left ... \right pair creates a so-called "math-inner" item. What's inside a math-inner item is, well, not "visible" to the outside world. In particular, the & character cannot be "seen" by the align environment. Since such code cannot be made to work, LaTeX is programmed to throw an error message and stop.

The following code will not throw an error message; however, the sizes of the parentheses may not be what you need:

x = y \left(5 + 3 \right. & \left. + 1\right)

The upshot? Don't overuse left and right! Fortunately, sizing large parentheses manually is not that difficult to accomplish.

Best Answer

Related Solutions

[Tex/LaTex] Inserting evil red code in LyX in mathmode

[Tex/LaTex] How to implement an ‘&’ inside a \left( \right) environment

Related Question