Order of Evaluation

Expressions are usually evaluated from left to right.

For example,

    10 -  3  +  2
   └───┬───┘
       │
       │
       7     +  2
      └──────┬───┘
             │
             │
             9

In other words, the value of: 10 - 3 + 2 is: 9.

But some operations are given priority over others. The rules are generally the same as in ordinary algebra. For example, multiply (*) has a higher priority than subtract (-).

    10 -  3  *  2
         └───┬───┘
             │
    10 -     6
   └─────┬────┘
         │
         4

In other words, the value of: 10 - 3 * 2 is: 4.

We shall discuss the rules of priority again in Reading 2 in Priority of Operators.