Faster way of writing \mathbf

Question

Is there a quicker way of doing boldface in math mode instead of typing out \mathbf{} each time? (It gets cumbersome when you denote simple vectors with boldface...)

Answer 1

There's a really cheesy way of saving keystrokes that is no longer than Todd's answer but just as comprehensive as Yiannis's:

\documentclass{article}

\def\*#1{\mathbf{#1}}

\def\ab{ab}
\begin{document}
 $\*v, \*w, \*\ab, \*\Gamma$.
\end{document}

Explanation: a control sequence whose name is a non-letter doesn't require either spaces or braces after it (unless of course you want it to act on multiple tokens, like plain ab; a macro such as my \ab will work just fine, though).

Answer 2

Just to expand on Todd Lehman's answer, you can save a bit of typing in the definitions, by automating the creation of the commands:

The LaTeX kernel has a looping construct named \@tfor that enables parsing a list of characters. We leverage this to define commands of the form \Va..\Vz and \VA..\VZ automatically using \csname..\endcsname.

\@tfor\next:=abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ\do{%
  \def\command@factory#1{%
    \expandafter\def\csname V#1\endcsname{#1}
  }
 \expandafter\command@factory\next
}

The full MWE is shown below:

\documentclass{article}
\makeatletter
\@tfor\next:=abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ\do{%
  \def\command@factory#1{%
    \expandafter\def\csname V#1\endcsname{#1}
  }
 \expandafter\command@factory\next
}
\makeatother
\begin{document}
\[ a \cdot (\Vv \otimes \Vw) = (a \cdot \Vv) \otimes \Vw = \Vv \otimes (a \cdot \Vw) \]
\end{document}

To have bold greek, we can use a similar technique. This time we will put all the greek letters in a comma delimited list, like:

 alpha,beta,gamma,zeta...Alpha...Zeta

we can then iterate over it, this time using a @for loop, here is the amended minimal.

\documentclass{article}
\usepackage{amsmath}
\usepackage{mathpazo}

\makeatletter
\@tfor\next:=abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ\do{%
  \def\command@factory#1{%
    \expandafter\def\csname V#1\endcsname{\mathbb{#1}}
  }
 \expandafter\command@factory\next
}
\begin{document}
\[ a \cdot (\Vv \otimes \Vw) = (a \cdot \Vv) \otimes \Vw = \Vv \otimes (a \cdot \Vw) \]

\def\greekvectors#1{%
 \@for\next:=#1\do{%
    \def\X##1;{%
     \expandafter\def\csname V##1\endcsname{\boldsymbol{\csname##1\endcsname}}
     }
   \expandafter\X\next;
  }
}

\greekvectors{alpha,beta,iota,gamma,lambda,nu,eta,Gamma,varsigma}

 $\VGamma\Viota\Valpha\Vnu\Vnu\Veta\Vvarsigma$
\end{document}

Will output

Answer 3

What you want is not necessarily a faster way to write \mathbf{v}, but a faster way to obtain the vector v, yes?

In this case, I would define a set of very short letter-specific macros, one for each vector variable. For example:

\documentclass{article}
\newcommand{\Vu}{\mathbf{u}}
\newcommand{\Vv}{\mathbf{v}}
\newcommand{\Vw}{\mathbf{w}}
\newcommand{\Vx}{\mathbf{x}}
\newcommand{\Vy}{\mathbf{y}}
\newcommand{\Vz}{\mathbf{z}}
\begin{document}
\[ \|\Vx\| = \sqrt{\Vx_1^2 + \cdots + \Vx_n^2} \]
\[ a(\Vu+\Vv) = a\Vu + a\Vv \]
\[ a_1\Vv_{i_1} + a_2\Vv_{i_2} + \cdots + a_n\Vv_{i_n} = 0 \]
\[ a \cdot (\Vv \otimes \Vw) = (a \cdot \Vv) \otimes \Vw = \Vv \otimes (a \cdot \Vw) \]
\end{document}

Answer 4

You can define a \newcommand*{\V}[1]{\mathbf{#1}}, then you can just write \V{x}:

\documentclass{article}
\usepackage{amsmath}
\newcommand*{\V}[1]{\mathbf{#1}}%
\begin{document}
    $\mathbf{x} \V{x}$
\end{document}

Answer 5

Define a command that takes an argument. No need to use a non-letter name: If your vector names are a single letter, you don't need to type the braces:

\newcommand\V[1]{\ensuremath{\mathbf{#1}}}

 \[ \V w = a\V v_0 + \V u  \]

You do need a space after \V (unless you use a non-letter instead of V).

Answer 6

When automating tex (speeding-up workflow is a particular case) — there's always two approaches:

1. automate the problem in tex
2. automate the problem in text-editor

When talking about minimising key strokes — you can't get shorter then a single key stroke, and that is possible with automating text-editor.

For example, here's an Emacs function which does what you want:

(defun tex-make-vector ()
  "If there's a selection -- wrap this with '\mathbf{' and '}'
   and put the point to the end.  Otherwise -- put the point
   between '\mathbf{' and '}'

   Also: when not in math mode -- enclose the thing in dollars."

  (interactive)

  (let (start end
              (delim "")
              (jump 1)
              )

    (when (not (texmathp))
      (setq delim "$")
      (setq jump 2)
      )

    (if (use-region-p)
        (progn
          (setq start (region-beginning))
          (setq end (region-end))

          (narrow-to-region start end)

          (goto-char (point-min))
          (insert (concat delim "\\mathbf{"))

          (goto-char (point-max))
          (insert (concat "}" delim))
          (widen)
          )

      (progn
        (insert (concat delim "\\mathbf{}" delim))
        (backward-char jump)
        )
      )
))

You can bind it to a key:

(define-key LaTeX-mode-map (kbd "C-v") 'tex-make-vector)

and you'll be able to insert a vector with a single key stroke.

The bad thing with "automating with text-editor" is always the same: it is not as modular than defining a \newcommand and using it. But using the custom command can also be fastened with text-editor.