342 Chapter 7 Expressions and Assignment Statements
The semantics of an expression is determined in large part by the order of
evaluation of operators. The associativity and precedence rules for operators
in the expressions of a language determine the order of operator evaluation
in those expressions. Operand evaluation order is important if functional side
effects are possible. Type conversions can be widening or narrowing. Some
narrowing conversions produce erroneous values. Implicit type conversions,
or coercions, in expressions are common, although they eliminate the error-
detection benefit of type checking, thus lowering reliability.
Assignment statements have appeared in a wide variety of forms, including
conditional targets, assigning operators, and list assignments.REVIEW QUESTIONS
- Define operator precedence and operator associativity.
- What is a ternary operator?
- What is a prefix operator?
- What operator usually has right associativity?
- What is a nonassociative operator?
- What associativity rules are used by APL?
- What is the difference between the way operators are implemented in
C++ and Ruby? - Define functional side effect.
- What is a coercion?
- What is a conditional expression?
- What is an overloaded operator?
- Define narrowing and widening conversions.
- In JavaScript, what is the difference between == and ===?
- What is a mixed-mode expression?
- What is referential transparency?
- What are the advantages of referential transparency?
- How does operand evaluation order interact with functional side
effects? - What is short-circuit evaluation?
- Name a language that always does short-circuit evaluation of Boolean
expressions. Name one that never does it. Name one in which the pro-
grammer is allowed to choose. - How does C support relational and Boolean expressions?
- What is the purpose of a compound assignment operator?
- What is the associativity of Cās unary arithmetic operators?