How Do Operator Precedence and Associativity Relate to the Order of Evaluation in Programming?

Operator Precedence and Associativity: A Deeper Dive

In the world of programming, operator precedence and associativity play a crucial role in determining the order of operations. But who defines these rules and how do they relate to order of evaluation?

Operator Precedence and Associativity: The Definition

Contrary to popular assumption, operator precedence and associativity are not explicitly defined by standards like ANSI C11. Instead, they are implicitly inferred from the grammar of the language.

In C and C , the grammar rules dictate the order of operations. For instance, the rule for additive expressions (such as and -) indicates that multiplicative expressions (* and /) are subexpressions of additive expressions. This establishes the precedence of * and / over and -.

Similarly, the left-associativity rule for additive expressions specifies that x y z will be grouped as (x y) z.

Sequence of Evaluation: A Distinct Concept

Operator precedence and associativity do not directly determine the order of evaluation. They merely define the grouping of expressions. For example, f1() f2() * f3() is grouped as f1() (f2() * f3()) based on precedence. However, the functions f1(), f2(), and f3() can still be called in any order.

The Exceptions

Certain operators, like the logical OR operator (||), do impose a sequencing on operand evaluation to enable short-circuiting. However, such operators are explicitly defined in the language standard.

In Summary

While operator precedence and associativity are important concepts for understanding the order of operations, they are distinct from the order of evaluation. Programmer's understanding of associativity and precedence can aid in comprehension of the language's rules, leading to more precise and efficient coding practices.

The above is the detailed content of How Do Operator Precedence and Associativity Relate to the Order of Evaluation in Programming?. For more information, please follow other related articles on the PHP Chinese website!