LaTeX question about making command to write sets like {x | x^2 > 0}

betterthangauss · 2009-10-31 23:09:04

I would like to make a command to write sets with constraints, so in my LaTeX I could write something like

\SetWithConstraint{x}{x^2 > 0}

Instead of having to manually do

\left{x | x^2 > 0 \right}

Here is the initial command definition I put in my preamble:

\newcommand{\SetWithContraint}[2]{\left\{#1\,|\,#2\right\}}

It seemed to work pretty well at first, for example this comes out looking pretty good:

However, I would like a way to have the size of the | in the middle match the size of the braces enclosing the set definition. My results here using that command look horrible:

Does anyone know a good way to accomplish this? I'd really prefer my TeX files weren't cluttered with garbage regarding explicit layouts of individual characters. Thanks!

mathsyperson · 2009-10-31 23:47:37

You could cheat and use "\left|" to get a | that changes its length according to what it needs to be. You'd also need to match it with a null brace (?), by putting "\right." somewhere.

betterthangauss · 2009-11-01 00:09:10

Thanks. I completely forgot about being able to use the "." character in \left, \right commands as you suggested. It still doesn't look great like that, but it does match what I was asking for.. lol

Now the bar definitely looks too tall though, since it matched the size of the outer brace. I guess I should have asked if it's possible to make it the next size down from the size of the brace. Does anyone have a better idea for how to do this that doesn't have the limitations this command does?

\newcommand{\SetWithContraint}[2]{\left\{#1\,\left|\,#2\right.\right\}}

Is there a way to do this that wouldn't be considered cheating? Sorry if it's a noob question whose correct answer is "RTFM", but I haven't seen a good example of how to do this cleanly yet. Thanks again for the help, mathstyperson!

betterthangauss · 2009-11-01 00:31:14

math. Using \left to line up the | doesn't look right when the right side is small and the left side big

i.e., here's the code for the command:

\newcommand{\SetWithContraint}[2]{\left\{\,#1\ \left|\ #2\,\right.\right\}}

And if I use it like this:

\[
   \Defined
      {B_N}
      {\SetWithContraint
         {
            \SetMember
               {
                  \FiniteSum{a_i z^{n-i}}{i}{0}{n}
               }
               {
                  \Polynomials{\ComplexNumbers}{z}
            }
         }
         {
            FOO!
      }
   }
\]

I get

where \SetMember, \Defined, etc. are commands I made up to try to decouple the logic of the markup from the characters used to display it.

Ricky · 2009-11-01 06:06:34

It's a good command to have, but with a pretty long name. Reminds me of Java. I would recommend:

SetC

Personally in commands, the more lowercase the better so I would actually make it

setc

It's all about reducing the number of keystrokes (whilst maintaining readability).

betterthangauss · 2009-11-01 10:08:03

Ricky wrote:

It's a good command to have, but with a pretty long name. Reminds me of Java. I would recommend:
SetC
Personally in commands, the more lowercase the better so I would actually make it
setc
It's all about reducing the number of keystrokes (whilst maintaining readability).

When I'm coding something in any language, I only like to use short variable names for names defined in small scopes. For something global that's going to be used a lot to express the semantics of my paper, I'd much rather be as explicit as possible in my naming. I feel like if I stop writing a document and then come back a year later to make corrections or changes, I'll understand \SetWithConstraint more quickly than I will \SetC (maybe I'd think \SetC was a command for the set of complex numbers, for instance). I use the camel-case with uppercase first letters to try to keep my defined names from conflicting with the symbols AMS defines.

Math Is Fun Forum

#1 2009-10-31 23:09:04

LaTeX question about making command to write sets like {x | x^2 > 0}

#2 2009-10-31 23:47:37

Re: LaTeX question about making command to write sets like {x | x^2 > 0}

#3 2009-11-01 00:09:10

Re: LaTeX question about making command to write sets like {x | x^2 > 0}

#4 2009-11-01 00:31:14

Re: LaTeX question about making command to write sets like {x | x^2 > 0}

#5 2009-11-01 06:06:34

Re: LaTeX question about making command to write sets like {x | x^2 > 0}

#6 2009-11-01 10:08:03

Re: LaTeX question about making command to write sets like {x | x^2 > 0}

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