Argthtjtr

The physics package has the macros dv and pdv which are great but I have a small problem with them.

If an argument with parenthesis included right after them they eat the whole argument. If there is a space in between the argument everything works fine but I want to prevent this happening all together. I checked the documentation but couldn't find a solution. So an example would be

documentclass{article}

usepackage{physics}



begin{document}



    [dv{x}{t}(y^2-5) qquad dv{x}{t} (y^2-5) qquad dv{x}{t} ]



end{document}

I want the output of the equation on the left to be the same as the middle one.

That's because dv (which is a shorthand for derivative) is defined as

DeclareDocumentCommandderivative{ s o m g d() }

{ % Total derivative

    % s: star for flatfrac flat derivative

    % o: optional n for nth derivative

    % m: mandatory (x in df/dx)

    % g: optional (f in df/dx)

    % d: long-form d/dx(...)

Even if the optional g-type argument is given (as in your case) the command will scan further for an optional delimited d-type argument which is delimited by ( and ) (maybe not the best choice in a mathematical context). To circumvent this you have to redefine derivative to always flush #5 if it is present.

documentclass{article}

usepackage{physics}



DeclareDocumentCommandderivative{ s o m g d() }

{ % Total derivative

    % s: star for flatfrac flat derivative

    % o: optional n for nth derivative

    % m: mandatory (x in df/dx)

    % g: optional (f in df/dx)

    % d: long-form d/dx(...)

    IfBooleanTF{#1}

    {letfractypeflatfrac}

    {letfractypefrac}

    IfNoValueTF{#4}

    {

        IfNoValueTF{#5}

        {fractype{diffd IfNoValueTF{#2}{}{^{#2}}}{diffd #3IfNoValueTF{#2}{}{^{#2}}}}

        {fractype{diffd IfNoValueTF{#2}{}{^{#2}}}{diffd #3IfNoValueTF{#2}{}{^{#2}}} argopen(#5argclose)}

    }

    {fractype{diffd IfNoValueTF{#2}{}{^{#2}} #3}{diffd #4IfNoValueTF{#2}{}{^{#2}}}IfValueT{#5}{(#5)}}

}



begin{document}



[dv{x}{t}(y^2-5) qquad dv{x}{t} (y^2-5) qquad dv{x}{t} ]



end{document}

At the same time I'd like to note that the physics package does not really help me writing physics formulae and I'm usually much better off typing the stuff by hand using the amsmath macros.

The package physics abuses the possibilities afforded by xparse to define commands having very weird syntax.

For instance, if you want to typeset the standard frac{dx}{dt}, you have to type

dv{x}{t}

If you want instead frac{d}{dt}(f(t)) you type

dv{t}(f(t))

which is where the syntax is weird: the variable you differentiate with respect to is no longer the second mandatory argument, but the first and a mandatory argument is missing altogether.

Of course this is achieved by actually making the second braced argument optional, which breaks all standard LaTeX conventions.

It is very counterintuitive having the independent variable first when the “long form” is desired and second for the “short (Leibniz) form”.

How can you do? My best advice is to keep at arm's length from physics. It seems to provide many bells and whistles for typesetting math, but this is at the expense of syntax clarity.

If you are tied to the package, simply add a no-op; a simple one in this context is /:

documentclass{article}

usepackage{physics}



begin{document}



[

dv{x}{t}/(y^2-5) qquad dv{x}{t}/ (y^2-5) qquad dv{x}{t}

]



end{document}

Renewing the commands in this way probably does it:

documentclass{article}

usepackage{physics}

renewcommanddv[2]{derivative{#1}{#2}{}}

renewcommandpdv[3]{partialderivative{#1}{#2}{#3}{}}

begin{document}



    [dv{x}{t}(y^2-5) qquad dv{x}{t} (y^2-5) qquad dv{x}{t} ]



    [pdv{x}{t}{z}(y^2-5) qquad pdv{x}{t}{z} (y^2-5) qquad pdv{x}{t}{z} ]



end{document}

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