forest-trees.tex

% Use with package `forest`
\forestset{
  nice trees/.style={
    for tree={
      parent anchor=south,
      child anchor=north,
      align=center,
      base=top,
      inner sep=0pt,%, s sep=12pt,
      l=0ex,
      before typesetting nodes={% 
        %based on nice empty nodes - page 52 of the manual, 
        %used in Jason Zentz's answer: http://tex.stackexchange.com/a/216103/
        if content={}{
          for parent={
            for children={anchor=north},
            calign=fixed edge angles,
            calign angle=60,
          },
          shape=coordinate,
          calign=fixed edge angles,
          calign angle=60,
        }{},
        %% from http://tex.stackexchange.com/a/205311, 
        %% in order to reduce the width of triangles/roofs
        % if n children=0{delay=with translation}{}  
      },
    },
  },
}
\newcommand\tree[2][]{\begin{forest}
    nice trees,
    #1% optional argument here like 'for tree={s sep=20pt}'
    #2
\end{forest}}