Can't use "if" in tikzmath - undefined control sequence "ifpgfmathfloatparseactive"

Question

MWE (copied from TikZ manual):

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{math}

\begin{document}
\begin{tikzpicture}
  \tikzmath{
    int \x;
    for \k in {0,10,...,350}{
      if \k>260 then { let \c = orange; } else {
        if \k>170 then { let \c = blue; } else {
          if \k>80 then { let \c = red; } else {
            let \c = green; }; }; };
      {
        \path [fill=\c!50, draw=\c] (\k:0.5cm) -- (\k:1cm) --
        (\k+5:1cm) -- (\k+5:0.5cm) -- cycle;
      };
    };
  }
\end{tikzpicture}
\end{document}

This gives me the following error message:

! Undefined control sequence.
\tikz@math@if@@doifelse ...gfmathfloatparseactive 
                                                  \pgfmathfloattofixed {\pgf...
l.19   }

I have the same problem with other code that uses if in tikzmath and this also applies to TeX files that used to compile without problems some time ago. Is the current (MiKTeX) version of TikZ broken?

I'm using MikTeX 2.9 on Windows 10, packages have been updated a few minutes ago, just in case.

UPDATE: Just to make this clearer - even this simple tikzmath code gives the same error message.

\tikzmath{
  \x = 42;
  if \x == 42 then {
    {\fill (0,0) circle (1cm);};
  };
}

Answer 1

This is a bug in PGF/TikZ and should have been reported on the bugtracker. I did that for you and also fixed the bug. The workaround is also mentioned in the ticket https://sourceforge.net/p/pgf/bugs/517/

If you are not sure whether what you are observing is a bug or not, just try an example from the manual. If the example from the manual fails, it is definitely a bug.

Workaround

Just add

\usetikzlibrary{fpu}

to your preamble.