Though I don't quite get what you want, here is a solution (which hopefully fits your needs) using the pgfkeys-package. I made the captions in a way, that they can be labeled (using the label= key) but they don't use the \caption command internally. Also it doesn't use your command \leftpadding but the padding-key.
\documentclass[11pt,a4paper,oneside]{memoir}
\pagestyle{plain}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
%\usepackage{fontspec}
%\usepackage{changepage}
%\setmainfont[Mapping=tex-text]{Liberation Serif}
%\setsansfont[Mapping=tex-text]{Liberation Sans}
%\setmonofont[Mapping=tex-text]{Liberation Mono}
\usepackage{pgfkeys}
\makeatletter
\newif\if@placedleft
\newif\if@placedright
\newif\if@placedmiddle
\newif\if@placedcapused
\newif\if@placedscapused
\newif\if@placedlabused
\newdimen\@placedpadding
\newdimen\@placedrest
\pgfkeys{/placedt/.is family,/placedt,
default/.style={% change the default settings here
place=left,
stretch=1.4,
padding=1cm,
},
stretch/.estore in=\arraystretch,
place/.is choice,
place/left/.code=\@placedlefttrue\@placedrightfalse\@placedmiddlefalse,
place/right/.code=\@placedrighttrue\@placedleftfalse\@placedmiddlefalse,
place/middle/.code=\@placedmiddletrue\@placedleftfalse\@placedrightfalse,
padding/.estore in=\@placedpadding,
caption/.code=\@placedcapusedtrue\def\@placedcap{#1},
scaption/.code=\@placedscapusedtrue\def\@placedscap{#1},
label/.code=\@placedlabusedtrue\def\@placedlab{#1},
}
\newenvironment{placedtabular}[2][]{%
\par\medskip\noindent\begin{minipage}{\textwidth}%
\pgfkeys{/placedt, default, #1}%
\if@placedleft%
\@placedrest=\textwidth%
\advance\@placedrest by -\@placedpadding%
\hskip\@placedpadding%
\begin{minipage}{\@placedrest}%
\raggedright%
\else\if@placedmiddle%
\centering%
\else\if@placedright%
\@placedrest=\textwidth%
\advance\@placedrest by -\@placedpadding%
\begin{minipage}{\@placedrest}%
\raggedleft%
\fi\fi\fi%
\if@placedcapused%
\refstepcounter{table}%
\tablename~\thetable: \@placedcap%
\if@placedscapused%
\addcontentsline{lot}{table}{\@placedscap}%
\else%
\addcontentsline{lot}{table}{\@placedcap}%
\fi%
\if@placedlabused%
\label{\@placedlab}%
\fi%
\\[0.2\baselineskip]%
\fi%
\footnotesize\begin{tabular}{#2}%
}{
\end{tabular}%
\if@placedmiddle\else%
\end{minipage}%
\fi%
\end{minipage}%
}
\makeatother
\newcommand{\leftpadding}{1cm}
\begin{document}
\listoftables
\chapter{}
All Gaul is divided into three parts, one of which the Belgae inhabit, the Aquitani another, those who in their own language are called Celts, in our Gauls, the third. All these differ from each other in language, customs and laws. The river Garonne separates the Gauls from the Aquitani; the Marne and the Seine separate them from the Belgae.
\begin{placedtabular}[caption=Caption,label=tab:first]{|c|c|}
\hline
{Alfa}
& {Bravo}
\\\hline
{Charlie}
& {Delta}
\\\hline
\end{placedtabular}
\medskip\begin{adjustwidth}{\leftpadding}{0cm}
\raggedright{Caption}\\
\renewcommand*{\arraystretch}{1.4}
\footnotesize\begin{tabular}[c]{|c|c|}
\hline
{Alfa}
& {Bravo}
\\\hline
{Charlie}
& {Delta}
\\\hline
\end{tabular}
\end{adjustwidth}
\bigskip
Of all these, the Belgae are the bravest, because they are furthest from the civilization and refinement of [our] Province, and merchants least frequently resort to them, and import those things which tend to effeminate the mind.
\begin{placedtabular}[caption=Another Caption,label=tab:second]{|c|c|}
\hline
{Longer Echo}
& {Long Foxtrot}
\\\hline
{Golf}
& {Hotel}
\\\hline
\end{placedtabular}
\medskip\begin{adjustwidth}{\leftpadding}{0cm}
\raggedright{Another Caption}\\
\renewcommand*{\arraystretch}{1.4}
\footnotesize\begin{tabular}[c]{|c|c|}
\hline
{Longer Echo}
& {Long Foxtrot}
\\\hline
{Golf}
& {Hotel}
\\\hline
\end{tabular}
\end{adjustwidth}
\bigskip
They are the nearest to the Germans, who dwell beyond the Rhine, with whom they are continually waging war; for which reason the Helvetii also surpass the rest of the Gauls in valor.
\end{document}
EDIT: Note that I have slightly altered the above code.
Usage of the placedtabular-environment is just like a normal tabular except, that in the optional argument you can use a comma seperated key=value syntax. The following keys are alailable:
stretch: the value used for arraystretchplace: the placement of the table. Available are left, right and middlepadding: the space to the left or right margin with place=left or place=right, respectivelycaption: the caption used for the tablescaption: the table-name for the \listoftables, if not used caption is used. If caption is not used, this doesn't have any effect.label: the label used for referencing the table
When you use one of these keys in a placedtabular-environment, the effects are only local and don't affect any other table set with this environment.
From the aforementioned keys place, stretch and padding have a default value, which are set in between the brackets of default/.style={...} which is used inside the first call of \pgfkeys in the above MWE. There is also the comment 'change the default settings here'.
EDIT2: The below code is everything inbetween of \makeatletter and \makeatother and doesn't set 'table x.y' infront of the caption. Because of this, I also removed the label-key as referencing won't work with this.
\makeatletter
\newif\if@placedleft
\newif\if@placedright
\newif\if@placedmiddle
\newif\if@placedcapused
\newif\if@placedscapused
%\newif\if@placedlabused
\newdimen\@placedpadding
\newdimen\@placedrest
\pgfkeys{/placedt/.is family,/placedt,
default/.style={%
place=left,
stretch=1.4,
padding=1cm,
},
stretch/.estore in=\arraystretch,
place/.is choice,
place/left/.code=\@placedlefttrue\@placedrightfalse\@placedmiddlefalse,
place/right/.code=\@placedrighttrue\@placedleftfalse\@placedmiddlefalse,
place/middle/.code=\@placedmiddletrue\@placedleftfalse\@placedrightfalse,
padding/.estore in=\@placedpadding,
caption/.code=\@placedcapusedtrue\def\@placedcap{#1},
scaption/.code=\@placedscapusedtrue\def\@placedscap{#1},
}
\newenvironment{placedtabular}[2][]{%
\par\medskip\noindent\begin{minipage}{\textwidth}%
\pgfkeys{/placedt, default, #1}%
\if@placedleft%
\@placedrest=\textwidth%
\advance\@placedrest by -\@placedpadding%
\hskip\@placedpadding%
\begin{minipage}{\@placedrest}%
\raggedright%
\else\if@placedmiddle%
\centering%
\else\if@placedright%
\@placedrest=\textwidth%
\advance\@placedrest by -\@placedpadding%
\begin{minipage}{\@placedrest}%
\raggedleft%
\fi\fi\fi%
\if@placedcapused%
\@placedcap%
\if@placedscapused%
\addcontentsline{lot}{table}{\@placedscap}%
\else%
\addcontentsline{lot}{table}{\@placedcap}%
\fi%
\\[0.2\baselineskip]%
\fi%
\footnotesize\begin{tabular}{#2}%
}{
\end{tabular}%
\if@placedmiddle\else%
\end{minipage}%
\fi%
\end{minipage}%
}
\makeatother
EDIT3: Complete code (without label and without the Table x.y: prefix) which includes two more options:
font are fontswitches applied to the table (stuff like \bfseries, \footnotesize or \small)captionfont are fontswitches applied to the caption
Both have the default to no change to surrounding fontswitches. If used both reset size and font and apply the argument provided.
\documentclass[11pt,a4paper,oneside]{memoir}
\pagestyle{plain}
\usepackage{fontspec}
%\usepackage{changepage}
\setmainfont[Mapping=tex-text]{Liberation Serif}
\setsansfont[Mapping=tex-text]{Liberation Sans}
\setmonofont[Mapping=tex-text]{Liberation Mono}
\usepackage{pgfkeys}
\makeatletter
\newif\if@placedleft
\newif\if@placedright
\newif\if@placedmiddle
\newif\if@placedcapused
\newif\if@placedscapused
\newif\if@placedfontused
\newif\if@placedcfontused
\newdimen\@placedpadding
\newdimen\@placedrest
\pgfkeys{/placedt/.is family,/placedt,
default/.style={%
place=left,
stretch=1.4,
padding=1cm,
},
stretch/.estore in=\arraystretch,
place/.is choice,
place/left/.code=\@placedlefttrue\@placedrightfalse\@placedmiddlefalse,
place/right/.code=\@placedrighttrue\@placedleftfalse\@placedmiddlefalse,
place/middle/.code=\@placedmiddletrue\@placedleftfalse\@placedrightfalse,
padding/.estore in=\@placedpadding,
caption/.code=\@placedcapusedtrue\def\@placedcap{#1},
scaption/.code=\@placedscapusedtrue\def\@placedscap{#1},
font/.store in=\@placedfont,
captionfont/.store in=\@placedcapfont,
font/.code=\@placedfontusedtrue\def\@placedfont{#1},
captionfont/.code=\@placedcfontusedtrue\def\@placedcapfont{#1},
}
\newenvironment{placedtabular}[2][]{%
\par\medskip\noindent\begin{minipage}{\textwidth}%
\pgfkeys{/placedt, default, #1}%
\if@placedleft%
\@placedrest=\textwidth%
\advance\@placedrest by -\@placedpadding%
\hskip\@placedpadding%
\begin{minipage}{\@placedrest}%
\raggedright%
\else\if@placedmiddle%
\centering%
\else\if@placedright%
\@placedrest=\textwidth%
\advance\@placedrest by -\@placedpadding%
\begin{minipage}{\@placedrest}%
\raggedleft%
\fi\fi\fi%
\if@placedcapused%
{\if@placedcfontused\normalsize\normalfont\@placedcapfont\fi\@placedcap}%
\if@placedscapused%
\addcontentsline{lot}{table}{\@placedscap}%
\else%
\addcontentsline{lot}{table}{\@placedcap}%
\fi%
\\[0.2\baselineskip]%
\fi%
\if@placedfontused\normalsize\normalfont\@placedfont\fi%
\begin{tabular}{#2}%
}{
\end{tabular}%
\if@placedmiddle\else%
\end{minipage}%
\fi%
\end{minipage}%
}
\makeatother
\newcommand{\leftpadding}{1cm}
\begin{document}
\listoftables
\chapter{}
All Gaul is divided into three parts, one of which the Belgae inhabit, the Aquitani another, those who in their own language are called Celts, in our Gauls, the third. All these differ from each other in language, customs and laws. The river Garonne separates the Gauls from the Aquitani; the Marne and the Seine separate them from the Belgae.
\begin{placedtabular}[caption=Caption,font=\bfseries]{|c|c|}
\hline
{Alfa}
& {Bravo}
\\\hline
{Charlie}
& {Delta}
\\\hline
\end{placedtabular}
\medskip\begin{adjustwidth}{\leftpadding}{0cm}
\raggedright{Caption}\\
\renewcommand*{\arraystretch}{1.4}
\footnotesize\begin{tabular}[c]{|c|c|}
\hline
{Alfa}
& {Bravo}
\\\hline
{Charlie}
& {Delta}
\\\hline
\end{tabular}
\end{adjustwidth}
\bigskip
Of all these, the Belgae are the bravest, because they are furthest from the civilization and refinement of [our] Province, and merchants least frequently resort to them, and import those things which tend to effeminate the mind.
\begin{placedtabular}[caption={Another\protect\\Caption}]{|c|c|}
\hline
{Longer Echo}
& {Long Foxtrot}
\\\hline
{Golf}
& {Hotel}
\\\hline
\end{placedtabular}
\begin{placedtabular}[caption=Another Caption]{|c|c|}
\hline
{Longer Echo}
& {Long Foxtrot}
\\\hline
{Golf}
& {Hotel}
\\\hline
\end{placedtabular}
\medskip\begin{adjustwidth}{\leftpadding}{0cm}
\raggedright{Another Caption}\\
\renewcommand*{\arraystretch}{1.4}
\footnotesize\begin{tabular}[c]{|c|c|}
\hline
{Longer Echo}
& {Long Foxtrot}
\\\hline
{Golf}
& {Hotel}
\\\hline
\end{tabular}
\end{adjustwidth}
\bigskip
They are the nearest to the Germans, who dwell beyond the Rhine, with whom they are continually waging war; for which reason the Helvetii also surpass the rest of the Gauls in valor.
\end{document}
Best Answer
It's a known issue. When you say
\raggedright, the command\\is redefined. This causes no harm until you want to terminate a table row: LaTeX finds the\\as defined by\raggedrightwhich doesn't mean the same thing as normally intabular. Writeand use
\newlineif you want to terminate a line in one of the cells. Or use your definition and terminate table rows with\tabularnewline.