Problem with nesting macros

I have written a macro to denote either the Fourier transformation (curly F by itself) or the Fourier transform of a function (curly F followed by a function and enclosed in left( and right) ). It does so by testing if the argument is equal to void or not:

newcommand*fourier[1]ensuremathmathscrFifthenelseequal#1!left(#1right)%

Therefore

fourier

fourierf(omega t)

give the expected results.

I wanted to apply fourier twice to a function and therefore wrote

fourierfourierf(x)

However, I'm getting a ! Missing endcsname inserted. error. How should I modify my macro so that it allows nesting? I'm guessing it's because of the ifthenelse construct?

! Missing endcsname inserted.

ifthenelse

2 Answers
2

Similar to Skillmon's original answer, but pretending to be mathtools and sticking to the mandatory argument. The starred version uses left/right, the unstarred version has an optional parameter for big/Big/...

mathtools

left

right

big

Big

Taking the approach to left and right from Mateus Araújo's answer to Spacing around left and right with help from Philipp Stephani (thanks to Ruixi Zhang for the suggestion in the comments)

left

right

documentclass[british]article usepackage[T1]fontenc usepackage[utf8]inputenc usepackagebabel usepackageamsmath usepackagemathrsfs usepackageifthen makeatletter DeclareRobustCommandfourier% mathscrF% @ifstar fourier@paren@star fourier@paren@expl newcommandfourier@paren@star[1]% ifrelaxdetokenize#1relax else mathopenmathcloseleft(#1right)% fi newcommandfourier@paren@expl[2]% ifrelaxdetokenize#2relax else mathopen#1(#2mathclose#1)% fi makeatother begindocument [ fourier ] [ fourierf(omega t) ] [ fourierfourierf(x) ] [ fourier*fourier*fracf^22pi(x) ] enddocument

enter image description here

That space ! before left and right though. Why not use the classic solution by Philipp Stephani: mathopenmathcloseleft( #1 right). For the fourier[big]... variants, I was wondering if there is a possible direct use of bigl and bigr. ;-)
– Ruixi Zhang
Sep 5 '18 at 15:56

!

left

right

mathopenmathcloseleft( #1 right)

fourier[big]...

bigl

bigr

@RuixiZhang Thanks for the hint. I had copied the left right bit from the OP. I'll see if I can find something that works for big->bigl/bigr, though I'm not sure if that is necessary when we already use mathopen and mathclose.
– moewe
Sep 5 '18 at 16:06

left

right

big

bigl

bigr

mathopen

mathclose

@RuixiZhang Given that bigl is just defbiglmathopenbig I don't think the conversion from big to bigl is really necessary here. If anyone is interested I came up with newcommandfrde@size@getlr[3]csnameexpandafter@gobblestring#1#2endcsname#3 which you can use as frde@size@getlrbigl( to get bigl(.
– moewe
Sep 5 '18 at 19:26

bigl

defbiglmathopenbig

big

bigl

newcommandfrde@size@getlr[3]csnameexpandafter@gobblestring#1#2endcsname#3

frde@size@getlrbigl(

bigl(

You are right. Unlike the “simple wrapper” from mathtools which does @nameuse MH_cs_to_str:N ##1 l #2 and @nameuse MH_cs_to_str:N ##1 r #3, going this extra mile to get bigl( just seems convoluted.
– Ruixi Zhang
Sep 5 '18 at 19:47

mathtools

@nameuse MH_cs_to_str:N ##1 l #2

@nameuse MH_cs_to_str:N ##1 r #3

bigl(

@FrédéricDelacroix Many expert users prefer the explicit size commands over the automatic sizing with left/right because the automatic commands may pick out sizes that are unnecessarily large or too small in certain situations (there is even a quote from the TeXbook that acknowledges that and it is reproduced in an answer here, but I can't find that right now).
– moewe
Sep 6 '18 at 8:13

left

right

I'd use the following:

ensuremath

ifthenelse

ifrelaxdetokenize#1relax

I've made a mistake therefore the former code grabbed the arguments wrong. The following uses xparse to grab the arguments in a more robust way. It therefore doesn't use the ifrelaxdetokenize#1relax test but xparse's IfValueT.

xparse

ifrelaxdetokenize#1relax

xparse

IfValueT

Results:

documentclassarticle usepackagemathrsfs usepackagexparse NewDocumentCommand fourier o % mathscrFIfValueT#1!left(#1right)% % begindocument $fourier[fourier[f]](x)$ enddocument

enter image description here

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