Math & Science ⇒ Underbracket macro with color

[Cham]

I need to write a simple macro to automatize equation writings, like the one below :

Code: Select all

Code, edit and compile here:

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\documentclass[12pt,letterpaper]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\usepackage{xcolor}
\begin{document}
A simple test :
    \begin{align*}
        A = \color[gray]{0.4}{\underbracket[0.5pt][4pt]{\color{black} BCD}_{pq - st}}\color{black} \, EFG &= KLM \\[6pt]
        &= ABC \color[gray]{0.4}{\underbracket[0.5pt][4pt]{\color{black} PQ}_{r s + u v}}\color{black} - MN.
    \end{align*}
\end{document}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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How should I write the macro to add any comment below some math item, with color (the example above uses a gray shade) ? I mean a macro command like

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\undercom{<color>}{<math item>}{<comment>}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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The <math item> should stay in black, and all math items after the commented one should stay in black too. The <comment> should be of the same color as the underbracket itself.

(sorry for my bad English, I hope the query is clear).

[Cham]

I defined the following macro, but I'm not sure it's the best way to do what I'm looking for.

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\newcommand*{\undercom}[3]{\color{#1}\underbracket[0.5pt][4pt]{\color{black}#2}_{#3}\color{black}}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Any suggestion or comments ?

[Cham]

No comments on the macro above ?

[cgnieder]

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\newcommand*{\undercom}[3]{\color{#1}\underbracket[0.5pt][4pt]{\color{black}#2}_{#3}\color{black}}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Any suggestion or comments ?

I would make three changes: 1) reset the color at the end of the macro, 2) make the color-resetting with \normalcolor instead of \color{black}, and 3) make the color selection optional with a default color:

Code: Select all

Code, edit and compile here:

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\documentclass[12pt,letterpaper]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\usepackage{xcolor}
\newcommand*{\undercom}[3][gray]{%
  \color{#1}%
  \underbracket[0.5pt][4pt]{\normalcolor#2}_{#3}%
  \normalcolor
}
\begin{document}
A simple test :
\begin{align*}
  A = \undercom{BCD}{pq - st} \, EFG
   &= KLM \\[6pt]
    &= ABC \undercom{PQ}{r s + u v} - MN.
\end{align*}
\end{document}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Run LaTeX here

Regards

[Cham]

Thanks for the reply !

Just by curiousity : why the normalcolor command, instead of the black color directive ? Is there any advantage ? (or inconvenience with the black color directive ?).

[cgnieder]

Well, the »normal« color could be redefined and then the black parts wouldn't fit any more:

Code: Select all

Code, edit and compile here:

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\documentclass[12pt,letterpaper]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\usepackage{xcolor}
% set ``normal'' color:
\color{blue}
\newcommand*{\undercom}[3][gray]{%
  \color{#1}%
  \underbracket[0.5pt][4pt]{\normalcolor#2}_{#3}%
  \normalcolor
}
\begin{document}
A simple test :
\begin{align*}
  A = \undercom{BCD}{pq - st} \, EFG
   &= KLM \\[6pt]
    &= ABC \undercom{PQ}{r s + u v} - MN.
\end{align*}
\end{document}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Run LaTeX here

Regards

[Cham]

Ok. Thanks a lot for your suggestions. I've adopted them.