\scalebox needs a number but you have passed it instructions to typeset a counter and then do some arithmetic to add 1 and assign that value to a counter, that is never going to work, you need to do the arithmetic fist then pass in the value.

@DavidCarlisle: I am trying to write a small package to solve my old problem tex.stackexchange.com/a/125722/19326. The idea is to automatically do some calculation and retireve the result to pass it to a scaling package like scalebox or adjustbox. I need csname for the retrival.

yes but as Steven shows below you need to pass the result not instructions to execute some arithmetic and assignments. internally it is count@=#1 which is fine if #1 is a number but if you pass it \the\mycount\relax \advance\mycount by 1 then it doesn't work.

The update code is missing loads of % from ends of lines, and if I understand you correctly you are passing tokens including \setcounter and \PackageWarning into the first argument which will put them in an \edef those commands can not possibly work in that context. The first argument of \scalebox is already expanded by \scalebox anything that you could put in an \edef can be passed as the argument to \scalebox so your redefinition does not do anything other than add spaces to the output.

@egreg: I am trying to wrap tex.stackexchange.com/a/125722/19326 into a package. The idea is to have an environment where I can do \addImage{someCode} to add an image and \getScale to get the factor by which the image should be scaled so that all pictures fill the row, and have equal height while keeping aspect ratios. I would like these two command so adjustbox scalbox or tikzscale can be used, depending on the situation. Take a look at github.com/coderinside/imageRow tp see what I got so far.

@DavidCarlisle I think I still have to get my head around tex, I am thinking a little bit in c-style here so to me int func{return 2;} and int func{int i=getOneSomehow(); return i+1;} are equal in the outcome of the program.

So is there someway that i can take an arbitrary defined command, execute it once and store its return in a way that it is save to pass to scalebox?

@ted tex is a macro expansion language so more like the c pre-processor than C, the analogy is not putttting a function there that returns an integer its like, in fact is putting a macro their that inlines the body of the function, That wouldn't work in c either in general

@DavidCarlisle regarding the missing %, I tried it out, the % is the minimum amount to have no extrawhitespace in the output. If I do \getIt\getIt I get two numbers with no space in between, e.g. 1.2349.034 (notice the second decimal dot, with space it would be 1.234 9.034)

@ted there is no return it os a macro language not a functional language, if you macro leaves a value in a register or another macro, then you can pass in that result, but in general there is no result or return from an arbitrary macro

Sorry about making you awnser twice but I was typing my second comment while your first came up

sry that is incomplete

@ted possibly (if you add the missing % and \else and \fi and if #1 is only ever a single token, and you add some code to define `\tmpvalue in the then and else branches

but why redefine scalebox rathe rthan just define a new command (which is 1000 times safer)

well i had some trouble getting the newline stuff in chat

but that is the idea

well my idea is the following:

@ted trick is to write multiline text somewhere else in an editor then paste it in and a "fixed format" button appears

shift+enter works as well

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@ted yes true it's stupidly counter-intuitive either way;-)

back to the idea: I have mutliple images in a row and want to make them all to have the same height

and scale them so that in total they fill for instance \linewidth

now the user might want to choose different scaling alternatives

i.e. scalebox tikzscale or adjustbox

@ted why?

Why what?

WHy different tools for scaling?

@ted they all are the same thing

well one is different

@ted ?

mirror.ox.ac.uk/sites/ctan.org/graphics/pgf/contrib/tikzscale/…

tikzscale

while the others scale the whole image

tikz scales the image but leaves the labels at fontsize

so if you draw an rectangle and label the corners, you scale the rectangle but the labels still have textsize

but maybe I jsut define two commands then

one for scalebox and one for tikzscale

@ted yes but only because tikz isn't an image, it's text. If you have external images then scaling is the only option

I think you helped me a lot

@ted \begingroup \endgroup aren't doing anything environments are a group

@ted and you need a % after the {}

@ted probably not although it's out of latex's control, the scaling happens in the back end, although similar concerns mean that \includegraphics actually uses two version of scaling for most back ends, if you just go [height= or scale= it passes the required scale factor to the back end as part of the image inclusion if the driver has that facility for that type, if it hasn't or if you have gone [angle=90] or other things as well as scaling then internally....

.... scalebox is used so the back end gets three calls instead of one, scale, image include, scale restore, I never new whether this made any difference in practice but it seemed the right thing to do at the time.