\newcommand question on “hatting” greek letters in one go

Question

I am working a lot with hatted indices such that

\( \hat{\mu} \)

A way to make this quicker would be to define the command.

\newcommand{\hmu}{\hat{\mu}}

but I would need to do this for pretty much every Greek letter separately. Is there a "nice" way to do this in one go? So for example, if I write \hrho it automatically understands \hat{\rho}?

Thanks in advance.

Answer 1

You can select a character that you don't need in math mode, make it active and define it to be the \hat command. In total you have to type the same number of characters as in your approach with a separate \h command for each Greek letter.

Put the following lines into the preamble of your document to use @ for this purpose.

\begingroup
  \lccode`~=`@
  \lowercase{\endgroup
    \let~\hat
  }%
\mathcode`@="8000

Then $@\alpha$ will produce an alpha with hat, whereas name@gmail.com outside of math-mode will still produce an @ sign. Here is an example.

\documentclass{article}
\begingroup
  \lccode`~=`@
  \lowercase{\endgroup
    \let~\hat
  }%
\mathcode`@="8000
\begin{document}
\( @\alpha@\beta@\mu \)

name@gmail.com
\end{document}

For an explanation, see Defining characters as macros

Answer 2

The following makes the definitions for the Greek letters that have a special macro (so not for o or an uppercase alpha) with a little less lines of code (a for loop over all the macro names):

\documentclass[]{article}

\makeatletter
\newcommand*\defhatgreek[1]
  {%
    \expandafter\newcommand\expandafter*\csname h#1\endcsname
      {\hat{\csname #1\endcsname}}%
  }
\@for\zz:=%
  {%
    alpha,beta,gamma,delta,epsilon,varepsilon,zeta,eta,theta,vartheta,kappa,%
    lambda,mu,nu,xi,pi,varpi,rho,varrho,sigma,varsigma,tau,upsilon,phi,varphi,%
    chi,psi,omega,%
    Gamma,Delta,Theta,Lambda,Xi,Pi,Sigma,Upsilon,Phi,Psi,Omega%
  }\do
  {%
    \expandafter\defhatgreek\expandafter{\zz}%
  }
\makeatother

\begin{document}
$\halpha + \hbeta = \hgamma + \hdelta$
\end{document}