mjhjmtu

I'd like to use the command foo with an optional argument to step and print the counter value iterated according to the number passed.

So, for example, foo[5] should step the counter 5 times, one by one.

(!) Note that it is not the same as stepcounter5.

MWE

documentclassreport

newcountermycount
setcountermycount0
newcommandfoostepcountermycountcounter is textbfthemycount

begindocument
first use: foo

second use: foo

now using with option to iterate: foo[2]

medskip

textitdesired output from line above should be:

medskip

now using with option to iterate: counter is textbf3,4

enddocument

With expl3 it's just a few lines.

documentclassreport
usepackagexparse

newcountermycount
setcountermycount0

ExplSyntaxOn
NewDocumentCommandfooO1
 
 int_compare:nT #1 > 0 
 
 int_compare:nTF #1 = 1 counter~is counters~are~
 stepcountermycount
 textbfthemycount
 prg_replicate:nn #1 - 1 ,stepcountermycounttextbfthemycount
 
 
ExplSyntaxOff

begindocument
first use: foo

second use: foo

now using with option to iterate: foo[2]

now using with option to iterate: counters are textbf3,4

foo[5]

enddocument

The trick is to do the first iteration and then proceed again adding first a comma.

If the number passed is zero or less nothing happens.

Here is short code with multido, xparse and etoolbox:

documentclassreport
usepackagemultido
usepackagexparse, etoolbox
newcountermycount
setcountermycount0
NewDocumentCommandfooO1counter is multidoi=1+1#1stepcountermycounttextbfthemycountifnumlessmultidocount#1,,.

begindocument

first use: foo

second use: foo

now using with option to iterate: foo[5]

enddocument

Here is an approach using multido for looping and a delayed delimiter definition:

documentclassarticle

usepackagemultido

newcountermycount

newcommandfoo[1][1]%
 counter%
 ifnum#1>1relax s areelse space isfi
 space
 % https://tex.stackexchange.com/a/89187/5764
 defitemdelimunskipspacedefitemdelim,space% Item delimiter delayed by one cycle
 bfseriesmultidoi=1+1#1itemdelim stepcountermycountthemycount%


begindocument

first use: foo

second use: foo

now using with option to iterate: foo[2]

medskip

textitdesired output from line above should be:

medskip

now using with option to iterate: counters are textbf3, 4

enddocument

With pgffor it is even less lines.

documentclassreport
usepackagepgffor
newcountermycount
setcountermycount0
newcommandfoo[1][1]counter is foreach X [count=Y] in
1,...,#1stepcountermycount%
textbfthemycountifnumY=#1%
else%
,fi

begindocument
first use: foo

second use: foo

now using with option to iterate: foo[2]

enddocument

A bit more code but without additional packages:

documentclassreport

newcountermycount
setcountermycount0

newcommandExchange[2]#2#1%
newcommandfoo[1][1]fooloop#1counter value is
makeatletter
newcommandfooloop[3]%
 ifnum#1>0 stepcountermycountfi
 ifnum#1>1 expandafter@firstoftwoelseexpandafter@secondoftwofi
 % 
 begingroup
 protected@edef@tempathemycount%
 c@mycount=#1relax
 advancec@mycount by -1relax
 expandafterendgroup
 expandafterfooloopexpandafter
 numberexpandafterc@mycountexpandafterexpandafter
 romannumeral0expandafterExchangeexpandafter@tempa #2, %
 counter values are%
 %
 #3 textbf#2themycount%
 %
%
makeatother

begindocument
first use: foo

second use: foo

now using with option to iterate: foo[4]

medskip

textitdesired output from line above should be:

medskip

now using with option to iterate: counter values are textbf3, 4, 5, 6

medskip

now using with option to iterate 0 times---counter is unchanged and displayed: foo[0]

medskip

now using with option to iterate -1 times---counter is unchanged and displayed: foo[-1]

enddocument