I would like to create custom macros with conditions. For example, I would like to add an "if-condition" to a macro that I created to write derivatives of any order in relation to a single variable. Here is the current code of my macro:

\newcommand{\drv}[3]{\dfrac{\df #2^#1}{\df #3^#1}}

The first argument #1 is the order of derivation, the second #2 the function that we take the derivative and the third #3 the variable of derivation. For example,


will give

enter image description here

I would like to change this code so that it don't display the derivation order #1 if it is equal to 1. But I don't know the syntax, this is why I need your help. I want to write something like

      if #1=1
         \dfrac{\df #2}{\df #3}
         \dfrac{\df ^#1 #2}{\df #3^#1}

Thank you for your help, have a good day.

  • @ChristianHupfer Thank you. I know but I would like to create my own macros, this is just a simple example to understand the use of conditions. – Loïc Jan 1 at 10:13
  • There already exist esdiff and diffcoeff packages which already can do that (and more: they consider the case of partial derivatives of any order). Why reinvent the wheel? – Bernard Jan 1 at 10:25
  • @Bernard the OP said this was just a specific example of a more general question about writing macros. – alephzero Jan 1 at 10:29
  • @Bernard I think the question of the OP goes more in the direction of 'How to create macros with conditions?' The derivative is just an example, so using a package will not help him in this case – caverac Jan 1 at 10:29
  • @Bernard thank you for introducing me to these packages. Indeed, I was mainly looking to know how to use "if-conditions", the derivation was only one example. – Loïc Jan 1 at 10:32

It's easy with xparse:


\newcommand{\df}{\mathop{}\!d} % use \mathrm{d} if you really prefer it





enter image description here

With o an optional argument is denoted; if it is present, \IfValueT{#1} will return true and use the argument as shown.

With the given definition, \df will behave as expected also in integrals, leaving a thin space before it when necessary.

  • 1
    Thank you, this is perfect. I just do not understand the use of \kern-\scriptspace. – Loïc Jan 1 at 10:53
  • @Loïc: \scriptspace is the amount of space inserted after a superscript and \kern<length> inserts horizontal space. Thus \kern-\scriptspace precisely cancels the space inserted between e.g. d^{n+1} and f. – Circumscribe Jan 1 at 19:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.