Explain the concept of operator precedence and why it's important to understand when writing ColdFusion expressions.

Operator precedence dictates the order in which operations are performed within a ColdFusion expression. It's a set of rules that determines which operations are evaluated first, second, and so on, ensuring consistent and predictable results. Without understanding operator precedence, expressions can be interpreted incorrectly, leading to unexpected and often erroneous outcomes. Think of it like the order of operations you learned in math class – PEMDAS (Parentheses, Exponents, Multiplication and Division, Addition and Subtraction) applies similarly in ColdFusion, although the specific order of operations differs slightly.

ColdFusion follows a specific hierarchy of operators. Higher precedence operators are evaluated before lower precedence operators. Here's a breakdown of the precedence order, from highest to lowest (though not every operator is listed, this covers the most common ones):

1. Parentheses ( ): Expressions within parentheses are always evaluated first. This allows you to explicitly control the order of operations. For example, `(2 + 3) * 4` evaluates 2 + 3 first, resulting in 5, then multiplies by 4, yielding 20. Without the parentheses, the result would be different.
2. Unary Operators: These operators act on a single operand. Examples include the logical NOT (!) and the negation operator (-). `!true` evaluates to false. `-5` negates the value 5.
3. Multiplicative Operators: These include multiplication (*), division (/), and modulus (%). They are evaluated from left to right. `10 / 2 * 3` is evaluated as (10 / 2) * 3, resulting in 15, not 30.
4. Additive Operators: These include addition (+) and subtraction (-). They are also evaluated from left to right. `5 + 2 - 1` is evaluated as (5 + 2) - 1, resulting in 6.
5. Concatenation Operator &: This operator joins strings together. It has lower precedence than additive and multiplicative operators. `5 & " apples"` results in "5 apples".
6. Relational Operators: These operators compare values, such as equality (==), inequality (!=), greater than (>), less than (<), greater than or equal to (>=), and less than or equal to (<=). They are evaluated before logical operators.
7. Equality Operators: These include equality (==) and inequality (!=). They are generally treated the same as relational operators.
8. Logical Operators: These operators combine boolean expressions. They include AND (&&), OR (||), and NOT (!). Logical operators are evaluated from left to right. `true && false || true` is evaluated as ((true && false) || true), resulting in true.

Understanding operator precedence is crucial for writing correct and maintainable ColdFusion code. Incorrect precedence can lead to subtle bugs that are difficult to track down. Using parentheses to explicitly define the order of operations is a best practice, even when the default precedence would produce the desired result. This improves code readability and reduces the risk of errors, especially in complex expressions. For instance, even though `2 + 3 * 4` would be evaluated as 2 + (3 * 4) (resulting in 14), writing it as `2 + (3 * 4)` clarifies the intended order and makes the code easier to understand.