Does there exists a version of \newcommand
, something like \extranewcommand{\foo}{bar}
which does defines \foo
to stand for bar
regardless of whether \foo
has been previously defined? Of course, if \foo
is undefined, one can use \newcommand{\foo}{bar}
, and if it is defined, one can use \renewcommand{\foo}{bar}
. However, in either case, one has to know which version to use: if one chooses wrong, the document won't compile. What I am interested in is if there exists a similar command (or perhaps a combination of commands, etc.) which will work in either situation.
As a rationalisation for the question, below are two situations in which I would find this command useful. Of course, the change is very minor, but it adds up over time, I think.
- One doesn't always know what commands are already defined. Sometimes, it happens that a newly defined command happens to also be something defined in some standard package. For instance, one wants to use
\operatorname{Im}
for the image of a linear operator, so it is convenient to declare\newcommand{\Im}{\operatorname{Im}}
. However,\Im
is already a fancy symbol for the imaginary part, so arenewcommand
is needed instead. I never use the mentioned imaginary part symbol, so it would be nice if I could just forget that it exists (but I can't). (Of course, this issue can be solved by compiling, noticing the error and adding "re" in front of "newcommand"; but, there are a lot of other such clashes that happen.) - I use a lot of commands used only "locally" (I'm not sure if it's a good coding practice, but I find it useful). For example, if I have a set S which occurs in many places in the text, I would often declare
\newcommand{\Set}{S}
or even\newcommand{\S}{S}
, so that I can easily change the symbol S to another one if I feel like it. This potentially leads to renewing commands quite frequently, which is not that much of a problem. However, if a block of text with a\newcommand
moves, then also a prefixre
has to move. (Again, it is not much of a problem, but I find it a nuisance).
Best Answer
There is
\providecommand
that defines a macro if it is not yet defined. Together with\renewcommand
you have your "\extranewcommand
":Or you can switch to the plain TeX primitives (other syntax!), e.g.:
(
\renewcommand
and friends without star use\long\def
and if the star form is given,\def
without\long
is used. Also the parameters are specified differently.)\declarecommand
A definition of the "requested"
\declarecommand
that calls\providecommand
and\renewcommand
together:Result: