绘制交换图

Question

交换图有几种代码，但我找不到下图的任何代码：

Answer 1

\documentclass[a4paper,12pt]{article}
\usepackage{tikz-cd}

\begin{document}
\begin{tikzcd}
L \arrow[dd, "\forall \delta"'] \arrow[rr, "\varepsilon"] &  & U(L) \arrow[lldd, "\exists ! f"] \\
 &  &  \\
D &  & 
\end{tikzcd}
\end{document}

Answer 2

代码语法与 nice 略有不同塞巴斯蒂亚诺回答：-）

\documentclass[border=3mm]{standalone}
\usepackage{tikz-cd}

\begin{document}
%---------------------------------------------------------------%
\begin{tikzcd}[column sep=large, row sep=large]
    L
    \arrow{r}{\varepsilon}  
    \arrow[swap]{d}{\forall\delta}           
&
    U(L)
    \arrow{dl}{\exists ! f}   \\     
%
    D
&
\end{tikzcd}
\end{document}