They are nested, and in every level there can be no more than one operation. Here is an example of a formula with many group operations: &quot; size 12 colour red font sans size -5 (a + size 8 b) &quot; like &quot; {size 12{colour red{font sans{size -5 (a + {size 8 b})}}}} &quot; . This example formula is then interpreted from left to right.
将序列中的组合运算视为：每个单一运算前后均加上花括号。它们是嵌套的，并且在每一层级中不能有一项以上的运算。以下是一个具有多项组合运算的公式示例： &quot; size 12 color red font sans size -5 (a + size 8 b) &quot; 类似于 &quot; {size 12{color red{font sans{size -5 (a + {size 8 b})}}}} &quot; 。