I'm having a problem with horizontal lines, \multicolumn and \cdashline.
As you can see in my MWE, I use \multicolumn to put section headings which I close by \cdashline but the vertical lines don't begin after the \cdashline.
I don't understand how to fix this problem!
\documentclass[pagesize,12pt,bibtotoc,pointlessnumbers, normalheadings, twoside]{book}
\usepackage[twoside=true]{geometry}
\usepackage{longtable}
\usepackage{array, makecell, multirow, tabularx}
\usepackage{arydshln}
\usepackage{booktabs}
\begin{document}
\section{I verbi e i loro tempi (1)}\index{Verbi!Tempi verbali|see {Infissi}}
\begin{longtable}[]{@{}
p{.18\linewidth}
>{\itshape}p{.26\linewidth}|
p{.18\linewidth}
>{\itshape}p{.26\linewidth}@{}}
\multicolumn{4}{c}{Infisso \textbf{-LI-} Passato semplice o remoto}\\
\bottomrule
\cdashline{1-4}[.4pt/1pt]
Ni-\textbf{li}-vaa&Indossai&Tu-\textbf{li}-vaa&Indossammo\\
U-\textbf{li}-vaa &Indossasti& M-\textbf{li}-vaa &Indossaste\\
A-\textbf{li}-vaa &Indoss\`{o}&Wa-\textbf{li}-vaa &Indossarono\\
\bottomrule
\multicolumn{4}{c}{Infisso \textbf{-NA-} Presente: azione~in corso di svolgimento}\\
\cdashline{1-4}[.4pt/1pt]
Ni-\textbf{na}-vaa &Sto indossando& Tu-
\textbf{na}-vaa&Stiamo indossando\\
U-\textbf{na}-vaa &Stai indossando& M-\textbf{na}-vaa&State indossando\\
A-\textbf{na}-vaa &Sta indossando& WA-\textbf{na}-vaa&Stanno indossando\\
\bottomrule
\multicolumn{4}{c}{Infisso \textbf{-A-} Presente: tempo imprecisato}\\
\cdashline{1-4}[.4pt/1pt]
N-\textbf{a}-vaa &Indosso&Tw-\textbf{a}-vaa &Indossiamo\\
W-\textbf{a}-vaa &Indossi& Mw-\textbf{a}-vaa &Indossate\\
\textbf{a}-vaa &Indossa& W-\textbf{a}-vaa &Indossano\\
\bottomrule
\multicolumn{4}{c}{Infisso \textbf{-TA-} Futuro}\\
\cdashline{1-4}[.4pt/1pt]
Ni-\textbf{ta}-vaa &Indosser\`{o} &Tu-\textbf{ta}-vaa &Indosseremo\\
U-\textbf{ta}-vaa &Indosserai & M-\textbf{ta}-vaa &Indosserete\\
A-\textbf{ta}-vaa &Indosser\`{a} & WA-\textbf{ta}-vaa&Indosseranno\\
\bottomrule
\multicolumn{4}{c}{Infisso \textbf{-ME-} Cambiamento di stato}\\
\cdashline{1-4}[.4pt/1pt]
Ni-\textbf{me}-vaa &Ho indossato&Tu-\textbf{me}-vaa & Abbiamo indossato\\
U-\textbf{me}-vaa &Hai indossato& M-\textbf{me}-vaa &Avete indossato\\
A-\textbf{me}-vaa & Ha indossato& WA-\textbf{me}-vaa &Hanno indossato\\
\bottomrule
\multicolumn{4}{c}{Prefisso \textbf{HU-} Abituale}\\
\cdashline{1-4}[.4pt/1pt]
\textbf{Hu}-vaa & Indosso, Indossa, ecc. &\textbf{Hu}-vaa &Indosso, Indossa, ecc. \\
\bottomrule
\multicolumn{4}{c}{\textbf{Pref.-}Radice\textbf{-E} Congiuntivo}\\
\cdashline{1-4}[.4pt/1pt]
Ni-va-\textbf{e}&(che) io indossi&Tu-va-
\textbf{e}&(che) noi indossiamo\\
U-va-\textbf{e}&(che) tu indossi& M-va-\textbf{e}&(che) voi indossiate\\
A-va-\textbf{e}&(che) egli indossi& WA-va-
\textbf{e}&(che) essi indossino\\
\bottomrule
\caption{I verbi e i loro tempi semplici}
\end{longtable}
\label{verbi-tempi-semplici}
\end{document}
Best Answer
Looking at your MWE, the issue seems to be with the
\bottomrulecommand. Indeed, as mentioned by Bernard's answer here, there is a compatibility issue betweenbooktabsand using vertical rules . A simple hack would be to replace your\bottomrulecommands with\hrulecommands.So the longtable in your MWE would be (note that I replaced the first bottom rule by a top rule, as in your MWE it was overlapping with the first dotted line):