n進数から10進数への変換式をlatexで作成.
test.tex
\documentclass{article}
\usepackage{xstring}
\usepackage{xifthen}
\usepackage{pgf}
\usepackage{amsmath} % align
\begin{document}
\newcounter{ep}
\newcounter{index}
\newcommand{\toD}[2][2]{
\StrLen{#2}[\mystrlen]
\setcounter{ep}{\mystrlen}
\setcounter{index}{0}%
\whiledo{\value{index} < \mystrlen}{%
\addtocounter{ep}{-1}
\stepcounter{index}%
\StrChar{#2}{\theindex} \times #1^\theep
\ifnum\theep>0{{}+{}}\fi
}
}
\newcommand{\toDD}[2][2]{
\StrLen{#2}[\mystrlen]
\setcounter{ep}{\mystrlen}
\setcounter{index}{0}%
\whiledo{\value{index} < \mystrlen}{%
\addtocounter{ep}{-1}
\stepcounter{index}%
\StrChar{#2}{\theindex} \times
\pgfmathint{#1^\theep}\pgfmathresult
\ifnum\theep>0{{}+{}}\fi
}
}
\begin{align}
(0334)_8 &= \toD[8]{0334} \\
&= \toDD[8]{0334} \\
%
(1011011)_2 &= \toD{1011011} \\
&= \toDD{1011011}
\end{align}
\end{document}
こうなります.