What's the Difference Between Operator Precedence and Operand Evaluation Order?

What is the Relation Between Operator Precedence and Order of Evaluation?

In programming, operator precedence refers to the order in which operations are performed based on the priority of their operators. Order of evaluation, on the other hand, pertains to the sequence in which operands are evaluated before applying the operators. While these concepts are often closely interrelated, they are not mutually dependent.

Considering the example of x

Likewise, precedence does not dictate the evaluation order in cases like x*y z. The standard allows for the possibility that z is evaluated before x or y. This flexibility ensures efficient code execution on stack machines or other architectures that support parallel processing of operands.

Moreover, the order of evaluation remains independent even in the presence of side effects. Side effects are handled by a separate thread that executes the operations asynchronously, joining with the main execution at sequence points (e.g., end of the expression).

Therefore, while operator precedence influences the sequence of operations, it does not determine the order of operand evaluation. The latter is determined by the underlying implementation and may vary depending on the architecture and compiler optimizations.

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