In version 4, I used to be able to write the equivalent of \mathrm{d}^4 x as \dl^4 x. However in version 5 I get and error about a "Missing { inserted". Is there a way to fix the problem?
MWE:
\documentclass[letterpaper,12pt]{article} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage[english]{babel} \usepackage{diffcoeff} \begin{document} \begin{equation} \dl^4 x \end{equation} \end{document} In v5 of diffcoeff the differential as a whole can be raised to a power, but to raise the operator symbol, the d, to a power you need to use the \difc (`c' for compact-form derivative) command. Thus \difc[4]x{{}} gives what you want, but I imagine uses more keystrokes than desired. To reduce the keystrokes, call a new macro (say) \dfl and write
\NewDocumentCommand \dfl { E{^}{1} m } { \difc[#1]{#2}{{}} } Then \dfl^4 x will give what you want (and \dfl x will give dx).
\dfl doesn't inherit the horizontal space on the left from \dfl. What's the equivalent of, say, \difdef { l } {} { outer-Ldelim = \onemu }? \difc with the desired space in the definition of \dfl: \difc like \difdef { c } { dfl } { outer-Ldelim=\onemu, outer-Rdelim=\nilmu} and change the definition of \dfl slightly: \NewDocumentCommand \dfl { E{^}{1} m } { \difc[#1]{#2}{{}} [] where I've added empty square brackets at the end. You can use the old version as [=v4] I couldn't see if there is a supported syntax in the new version
\documentclass[letterpaper,12pt]{article} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage[english]{babel} \usepackage{diffcoeff}[=v4] \begin{document} \begin{equation} \dl^4 x \end{equation} \end{document} 
So, you need to use a completely different command, \difc, just to typeset this? And this package uses dots of all things as argument delimiters (yes, I know many people feel the same way about g-type arguments, but I respectfully disagree)? This is a classical example of why I prefer keyval syntax, such as the following (I used my own package to make this, but this should be taken as an encouragement to the authors of diffcoeff, derivative, and other packages to embrace keyval syntax):
\documentclass{article} \usepackage{semantex} \NewVariableClass\DifferentialOperator[ bool provide=in pars, define keys={ {in pars}{ use par=false, bool set true=in pars, set arg dots={\dotsc}, set arg sep={,}, }, {not in pars}{ use par=never, bool set false=in pars, set arg dots={\dotsm}, set arg sep={\,}, }, }, not in pars, define keys[1]={ {pow}{upper={#1}}, }, prepend keys[1]={ {arg}{ bool if TF={in pars} { define arg keys[1]={ {default}{ sep={####1}, } }, }{ return, define arg keys[1]={ {default}{ set arg keys x={ other sep={% \SemantexDataGetExpNot{arg sep}% \SemantexDataGetExpNot{symbol}% }{% \SemantexExpNot{####1}% } }, } }, }, } }, ] \NewObject\DifferentialOperator\dl{d} \NewObject\DifferentialOperator\dlpartial{\partial} \begin{document} \begin{gather*} \dl = \dl{x} = \dl[pow=4] = \dl{x,y,z} = \dl[pow=4]{x,y,z} = \dl[u]{x,y,z} = \dl[u,pow=4]{x,y,...,z} \\ \dlpartial = \dlpartial{x} = \dlpartial[pow=4] = \dlpartial{x,y,z} = \dlpartial[pow=4]{x,y,z} = \dlpartial[u]{x,y,z} = \dlpartial[u,pow=4]{x,y,...,z} \\ \dl[in pars] = \dl[in pars]{x} = \dl[in pars,pow=4] = \dl[in pars]{x,y,z} = \dl[in pars,pow=4]{x,y,z} = \dl[u,in pars]{x,y,z} = \dl[u,in pars,pow=4]{x,y,...,z} \\ \SetupObject\dl{in pars} \dl = \dl{x} = \dl[pow=4] = \dl{x,y,z} = \dl[pow=4]{x,y,z} = \dl[u]{x,y,z} = \dl[u,pow=4]{x,y,...,z} \end{gather*} \end{document} 
