Level of Precedence

Each operator has an assigned level of precedence that determines when it will take action in relation to other operators within the same expression. For example, it is commonly known that Algebraic rules require multiply and divide operations to be performed before add and subtract operations. The multiply and divide operators are said to have a "higher level of precedence" than add and subtract. Additionally, multiply and divide are commutable; both are on the same precedence level, so their operations result in the same value regardless of the order it is performed (multiply first, then divide, or vice versa). Commutative operators are always evaluated left to right except where parentheses override that rule.

The Propeller chip applies the order-of-operations rules as does Algebra: expressions are evaluated left-to-right, except where parentheses and differing levels of precedence exist.

Following these rules, the Propeller will evaluate:

X = 20 + 8 * 4 – 6 / 2

...to be equal to 49; that is, 8 * 4 = 32, 6 / 2 = 3, and 20 + 32 – 3 = 49. If you wish the expression to be evaluated differently, use parentheses to enclose the necessary portions of the expression.

For example:

X = (20 + 8) * 4 – 6 / 2

This will evaluate the expression in parentheses first, the 20 + 8, causing the expression to now result in 109, instead of 49.

The Operator Precedence Levels Table indicates each operator's level of precedence from highest (level 0) to lowest (level 12). Operators with a higher precedence are performed before operators of a lower precedence; multiply before add, absolute before multiply, etc. The only exception is if parentheses are included; they override every precedence level.