Bsrgvty

My end goal is to highlight certain nodes depending on their value, and there will be quite a few of them so I need there to be a conditional in a for loop. I've tried the following MWE, but it doesn't do what I expect.

Essentially, I need to check if an integer is in a list of integers, and draw a node based on that.

documentclassarticle
usepackagetikz

begindocument
begintikzpicture
foreach x in 10, 9,..., 0

 ifcase x10
 or5
 node[] x;
 fi

endtikzpicture
enddocument

Edit: Question reworded for clarity after accepting answer.

if I understand the question correctly, you want to check whether or not a number is equal to A, B, C etc. This can be done as follows.

documentclassarticle
usepackagetikz

begindocument
begintikzpicture
foreach X in 10, 9,..., 0

pgfmathtruncatemacroitest
 ifnumitest=1
 node at (X,0) X;
 fi

endtikzpicture
enddocument

For more extensive applications I recommend the memberQ function, which may or may not become one day part of the pgf world. It tests if an integer is in a list of integers.

documentclassarticle
usepackagetikz

makeatletter
pgfmathdeclarefunctionmemberQ2%
 begingroup%
 edefpgfutil@tmpb0%
 edefpgfutil@tmpa#2%
 expandafterpgfmath@member@i#1pgfmath@token@stop
 edefpgfmathresultpgfutil@tmpb%
 pgfmath@smuggleonepgfmathresult%
 endgroup
defpgfmath@member@i#1%
 ifxpgfmath@token@stop#1%
 else
 ifnum#1=pgfutil@tmparelax%
 gdefpgfutil@tmpb1%
 %typeout#1=pgfutil@tmpa
 fi%
 expandafterpgfmath@member@i
 fi 
makeatother
begindocument
begintikzpicture
foreach X in 10, 9,..., 0

pgfmathtruncatemacroitestmemberQ(1,4,8,X)
 ifnumitest=1
 node at (X,0) X;
 fi

endtikzpicture
enddocument

ifcase doesn't work like the switch statement in other languages, in which you choose what values have a branch of their own. The syntax of ifcase is:

ifcase<number>
 <case 0>
or <case 1>
or <case 2>
or <as many as you want>
else <other cases>
fi

you can't skip a value. In your code you'd need:

foreach x in 10, 9,..., 0

 ifcasex relax
 % 0
 or % 1
 or % 2
 or % 3
 or % 4
 or % 5
 node[] x;
 or % 6
 or % 7
 or % 8
 or % 9
 or % 10
 else % other cases
 fi

which is a handful. For a small number of exceptions you could use ifnum:

foreach x in 10, 9,..., 0

 ifnumx=5 relax
 node[] x;
 elseifnumx=10 relax
 % do things with x=10
 else
 % possibly more cases
 fifi

which can become a mess, once you have more than a couple of cases.

My suggestion: int_case:nnF. You can specify each case individually and a false branch in case no other is taken:

documentclassarticle
usepackagetikz
usepackageexpl3
ExplSyntaxOn
cs_new_eq:NN IntCasennF int_case:nnF
ExplSyntaxOff
begindocument
begintikzpicture
foreach x in 10, 9,..., 0

 IntCasennF x
 
 5node[] x;
 10<Code for 10>
 
 <Other cases>

endtikzpicture
enddocument