\[ \newcommand{\tr}{\Rightarrow} \newcommand{\trs}{\tr^{\!\ast}} \newcommand{\rlnm}[1]{\mathsf{(#1)}} \newcommand{\rred}[1]{\xrightarrow{#1}} \newcommand{\rreds}[1]{\mathrel{\xrightarrow{#1}\!\!^*}} \newcommand{\cl}{\mathsf{Cl}} \newcommand{\pow}{\mathcal{P}} \newcommand{\matches}{\mathrel{\mathsf{matches}}} \newcommand{\kw}[1]{\mathsf{#1}} \]

Left association example

\[\begin{array}{l|l} \text{when we write...} & \text{we mean the tree...} \\\hline 5 - 4 + 1 & (5 - 4) + 1 \\ 1 + 3 - 6 & (1 + 3) - 6\\ 6 * 7 * 8 & (6 * 7) * 8\\ 1 + 1 + 2 & (1 + 1) + 2\\ 8 - 4 - 1 & (8 - 4) - 1 \end{array}\]