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Why does the following test using \ifthenelse not compile:

\documentclass[border=30pt, tikz]{standalone} \usepackage{tikz,tikz-3dplot} \usepackage{ifthen} \usepackage{animate, calc}%%%%%%%%%%%% \usepackage{animate} \usepackage{circuitikz} \begin{document} \foreach \x in {0.1,0.2,...,4}{ \begin{tikzpicture} \begin{circuitikz} \draw (0,0) to[V,v=$U_q$] (0,2) % The voltage source to[short] (2,2) to[R=$R_1$] (2,0) % The resistor to[short] (0,0); \draw (2,2) to[short] (4,2) to[R=$R_2$] (4,0) to[short] (2,0); \ifthenelse{\x<2}{\fill[color=red] (0,\x) circle (3pt);}{} \end{circuitikz} \end{tikzpicture} } \end{document}

On compilation I get the following error:

! Missing = inserted for \ifnum. <to be read again>
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It doesn't work, because \ifnum (which is what \ifthenelse calls) only takes whole numbers (no fractions). Therefore you need another test. A very simple attempt:

\documentclass[border=30pt, tikz]{standalone} \usepackage{tikz,tikz-3dplot} \usepackage{xparse} \usepackage{animate, calc}%%%%%%%%%%%% \usepackage{animate} \usepackage{circuitikz} \ExplSyntaxOn \NewDocumentCommand { \xifnum } { } { \fp_compare:nTF } \ExplSyntaxOff \begin{document} \foreach \x in {0.1,0.2,...,4}{ \begin{tikzpicture} \begin{circuitikz} \draw (0,0) to[V,v=$U_q$] (0,2) % The voltage source to[short] (2,2) to[R=$R_1$] (2,0) % The resistor to[short] (0,0); \draw (2,2) to[short] (4,2) to[R=$R_2$] (4,0) to[short] (2,0); \xifnum{\x<2}{\fill[color=red] (0,\x) circle (3pt);}{} \end{circuitikz} \end{tikzpicture} } \end{document}
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    Or using \foreach \x in {1,2,...,40} and comparing \x with 20, with (0,\x/10) as coordinate. Commented Apr 14, 2018 at 9:48
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    @egreg That sounds far too simple (and has no expl3) ;) Commented Apr 14, 2018 at 9:55
  • thank you for all, i used this reply to improve my question [about circuitikz ](tex.stackexchange.com/questions/426459/…) Commented Apr 14, 2018 at 10:23

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