# [Tex/LaTex] Arrow end type [-] unknown – even though library is loaded

tikz-arrowstikz-pgf

I am a beginner with LaTex and not comfortable enough to switch over just yet. At the moment I mainly use the smartdiagram package to easily produce high-quality flow diagrams for various documents and presentations.

For this use case I created a number of templates. Here are two examples based on them.

This one works:

\documentclass{article}
\usepackage{tikz} % smartdiagram base package
\usepackage{smartdiagram} % used for generating diagrams
\begin{document}
\smartdiagramset{
% ARROWS
arrow tip={stealth},
}
\smartdiagram[flow diagram:horizontal]{ % set orientation (horizontal/vertical)
A,B,C,D
}
\end{document}

This one doesn't:

\documentclass{article}
\usepackage{tikz} % smartdiagram base package
\usepackage{smartdiagram} % used for generating diagrams
\begin{document}
\smartdiagramset{
% ARROWS
arrow tip={|-|},
}
\smartdiagram[flow diagram:horizontal]{ % set orientation (horizontal/vertical)
A,B,C,D
}
\end{document}

As you can see I am struggling with the arrow library. If I set smartdiagram's arrow tip parameter to a bracket-like TikZ arrow, LaTex returns the following error message:

flow_diagram.tex.swp:119: Package pgf Error: Arrow
end type [-]'' unknown.

See the pgf package documentation for explanation.

I took this arrow definition from TikZ' manual (p. 257), where a number of bracket-like arrow tips and their respective names are listed.

Any other arrow tip type I can render with this template without any problems, it's only these bracket-type arrows I struggle with.

Can you please tell me, if I am doing something wrong?