Enabling FPU breaks drawing with arrows

[PhelypeOleinik]

The following code:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{fpu}
\begin{document}
\begin{tikzpicture}[/pgf/fpu=true,/pgf/fpu/output format=fixed]
  \draw (0,0) -- (1,1); % works
  \draw [->] (0,0) -- (1,1); % doesn't
\end{tikzpicture}
\end{document}

breaks with:

! Package PGF Math Error: Sorry, an internal routine of the floating point unit
 got an ill-formatted floating point number `-28.45274000000000'. The unreadabl
e part was near '-28.45274000000000'..

See the PGF Math package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.9   \draw [->] (0,0) -- (1,1);
                                 % doesn't
?

with the current (3.1.3) version of PGF--TikZ.

The command works fine without the [->]. PGF--TikZ version 3.1.1 works fine.

[hmenke]

Bisected to 65b8261

[hmenke]

What we have here is a much deeper problem, namely that drawing with FPU enabled will not work. Try this example with any version of PGF:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{fpu}
\begin{document}
\begin{tikzpicture}[/pgf/fpu=true]
  \draw (0,0) -- (1,1);
\end{tikzpicture}
\end{document}

I'm tending to mark this as wont-fix because even if we fix this tiny regression, the rest will still remain unusable.

[u-fischer]

Imho it indicates a real problem of the fpu library with output format fixed:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{fpu}
\begin{document}
\pgfkeys{/pgf/fpu,/pgf/fpu/output format=fixed}
\pgfmathcos{1}
xxx
\end{document}

[u-fischer]

It seems to work if one use \pgfmathparse instead of the math command:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{fpu}
\makeatletter
\def\pgfpointnormalised#1{%
  \pgf@process{#1}%
  \pgfmathparse{atan2(\the\pgf@y,\the\pgf@x)}%
  \let\pgf@tmp=\pgfmathresult%
  \pgfmathparse{cos(\pgf@tmp)}%
  \pgf@x=\pgfmathresult pt\relax%
  \pgfmathparse{sin(\pgf@tmp)}%
  \pgf@y=\pgfmathresult pt\relax%
  }
\begin{document}
\begin{tikzpicture}[/pgf/fpu=true,/pgf/fpu/output format=fixed]
  \draw (0,0) -- (1,1); % works
  \draw [->] (0,0) -- (1,1); % doesn't
\end{tikzpicture}
\end{document}

[hmenke]

I have a patch, but that will break other things.

diff --git a/tex/generic/pgf/math/pgfmathfunctions.code.tex b/tex/generic/pgf/math/pgfmathfunctions.code.tex
index d1c3c434..3f6e5784 100644
--- a/tex/generic/pgf/math/pgfmathfunctions.code.tex
+++ b/tex/generic/pgf/math/pgfmathfunctions.code.tex
@@ -71,7 +71,11 @@
         \def#1{#2}%
         \def\pgfmath@@head{\def#2}%
     \or
-        \def#1##1{\pgfmathparse{##1}\expandafter#2\expandafter{\pgfmathresult}}%
+        \def#1##1{%
+            \pgfmathparse{##1}%
+            \pgfmathfloatparsenumber{\pgfmathresult}%
+            \expandafter#2\expandafter{\pgfmathresult}%
+        }%
         \def\pgfmath@@head{\def#2####1}%
     \else%
         \pgfmath@toks={}%
@@ -91,7 +95,8 @@
             \pgfmath@addto@toks{\pgfmathparse}%
             \expandafter\expandafter\expandafter\pgfmath@addto@toks%
                 \expandafter\expandafter\expandafter{\expandafter\expandafter\expandafter%
-                    {\expandafter\pgfmath@char@hash\pgfmathcounter}}%
+                    {\expandafter\pgfmath@char@hash\pgfmathcounter}%
+                    \pgfmathfloatparsenumber{\pgfmathresult}}%
             \pgfmath@addto@toks{\let}%
             \expandafter\pgfmath@addto@toks\expandafter{%
                 \csname pgfmath@argument@\pgfmathcounter\endcsname=\pgfmathresult}%

[ilayn]

I enjoy the manual's warning about this instead of changing the behavior

Use fpu=false to deactivate the FPU. This will restore any change. Please note that this is not
necessary if the FPU is used inside of a TeX group – it will be deactivated afterwards anyway.
It does not hurt to call fpu=true or fpu=false multiple times.

I think a better warning about fpu not being a drop-in replacement math engine for the regular usage (which would have been the default if it was so) is a better way instead of enabling at the top of the tikzpicture and trying to mend things as they break.