\pgfmathparse returns a phantom .0.0

Question

\documentclass{minimal}
\usepackage{tikz}
\begin{document}
\pgfmathparse{random(-5,5)}
\pgfmathresult
\end{document}

Works, but I have a .0.0 that not supposed to be here.

Answer 1

From the PGF manual, section 90.2.6, page 942 (version 3.0.0)

random(x,y)
\pgfmathrandom{x,y}
This function takes zero, one or two arguments. If there are zero arguments, a uniform random number between 0 and 1 is generated. If there is one argument x, a random integer between 1 and x is generated. Finally, if there are two arguments, a random integer between x and y is generated. If there are no arguments, the PGF command should be called as follows: \pgfmathrandom{}.

What the manual doesn't say is that the arguments should be non negative. Indeed the simple document

\documentclass{article}
\usepackage{tikz}
\begin{document}

\pgfmathparse{random(-1,10)}

\end{document}

that should produce no text, creates the following output

If a random number between –1 and 10 is needed, just use

\pgfmathparse{random(1,12)-2}

This is to be considered a bug in the documentation.

Answer 2

I found something about this:

Firstly, pgf treats any calculation result as floating point number:

\pgfmathsetmacro{\a}{1 + 1};
\pgfmathsetmacro{\b}{-1};
\pgfmathsetmacro{\c}{1};
\draw (\px, \py) circle(2) node[anchor=north west]{\a,\b,\c};

So, this will produce 2.0, -1.0, 1, respectively (-1 is treated as calculating the negative of 1).

Then, passing floating point to random will result in .0 because random only takes the integer part.

Thus, we just use random(int(-10), int(10)), then the .0 disappears.