Programming Chapter 6: Expressions & Assignment
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Questions and Answers

What is the primary role of assignment statements in imperative languages?

  • To perform arithmetic calculations
  • To control flow in programs
  • To define functions and procedures
  • To specify computations and store values (correct)

    • A ternary operator has four operands.

    False

    What are arithmetic expressions composed of?

    Operators, operands, parentheses, and function calls.

    The operator precedence rules determine the order in which __________ are evaluated.

    <p>operators</p> Signup and view all the answers

    Match the following operator types with their number of operands:

    <p>Unary operator = One operand Binary operator = Two operands Ternary operator = Three operands</p> Signup and view all the answers

    Which of the following is NOT typical precedence level in arithmetic expressions?

    <p>Ternary operators</p> Signup and view all the answers

    Short-circuit evaluation is a principle applied to arithmetic expressions.

    <p>False</p> Signup and view all the answers

    List two design issues for arithmetic expressions.

    <p>Operator precedence rules, order of operand evaluation.</p> Signup and view all the answers

    Which relational operator is used in C to represent logical AND?

    <p>&amp;&amp;</p> Signup and view all the answers

    In C, Boolean expressions are evaluated as Boolean types.

    <p>False</p> Signup and view all the answers

    What does the expression 'a < b < c' evaluate to in C?

    <p>0 or 1 depending on the values of a and b.</p> Signup and view all the answers

    In C, the operator used for logical OR is ___ .

    <p>||</p> Signup and view all the answers

    Which of the following operators has the highest precedence in C?

    <p>Postfix ++</p> Signup and view all the answers

    Match the following programming languages with their short-circuit evaluation notation:

    <p>C = &amp;&amp; and || Ada = and then and or else Java = &amp;&amp; and || C++ = &amp;&amp; and ||</p> Signup and view all the answers

    Short-circuit evaluation will always evaluate all operands.

    <p>False</p> Signup and view all the answers

    What issue can arise from non-short-circuit evaluation in a condition such as '(index < length) && (LIST[index] != value)'?

    <p>Indexing problem when index equals length.</p> Signup and view all the answers

    What is operator overloading?

    <p>The use of an operator for more than one purpose</p> Signup and view all the answers

    Narrowing conversion can change a float to an int.

    <p>True</p> Signup and view all the answers

    What is a coercion in programming?

    <p>An implicit type conversion.</p> Signup and view all the answers

    In C, explicit type conversion is called __________.

    <p>casting</p> Signup and view all the answers

    What is a potential problem with user-defined overloaded operators?

    <p>They can introduce nonsense operations</p> Signup and view all the answers

    Match the following types of conversions with their descriptions:

    <p>Narrowing Conversion = Converts to a type that cannot include all original values Widening Conversion = Converts to a type that can include at least approximations of all original values Implicit Type Conversion = Occurs automatically without explicit instruction Explicit Type Conversion = Requires a specific command to change type</p> Signup and view all the answers

    All numeric types in most programming languages are coerced in expressions.

    <p>True</p> Signup and view all the answers

    Name one limitation of computer arithmetic.

    <p>Division by zero or overflow.</p> Signup and view all the answers

    Which of the following assignment operators is used in C, C++, and Java for equality?

    <p>=</p> Signup and view all the answers

    Conditional targets in C, C++, and Java allow the assignment of values based on a flag.

    <p>True</p> Signup and view all the answers

    What is the purpose of a compound assignment operator?

    <p>To provide a shorthand method of specifying commonly needed forms of assignment.</p> Signup and view all the answers

    In C, C++, and Java, the expression 'count++' is used to __________ the value of count.

    <p>increment</p> Signup and view all the answers

    Which assignment statement will not work in Ada due to no assignment coercion?

    <p>float c = 10.5; int d = c;</p> Signup and view all the answers

    The expression 'c = a / b' in mixed-mode assignments assigns an integer variable to a float regularly.

    <p>False</p> Signup and view all the answers

    What does the assignment statement 'while ((ch = getchar()) != EOF)' accomplish?

    <p>It reads a character from input and assigns it to ch while checking if the end of file has been reached.</p> Signup and view all the answers

    Match the following programming languages with their assignment syntax:

    <p>C = Standard assignment operator is = Pascal = Uses := for assignment Java = Handles widening assignment coercions Ada = No assignment coercions allowed</p> Signup and view all the answers

    Which of the following statements about operator associativity rules is true?

    <p>The ** operator associates right to left.</p> Signup and view all the answers

    In APL, all operators have different precedence levels.

    <p>False</p> Signup and view all the answers

    What is the result of the following expression if count is 0: average = (count == 0)? 0 : sum / count?

    <p>average = 0</p> Signup and view all the answers

    The order of operand evaluation starts with ______, followed by constants and then parenthesized expressions.

    <p>variables</p> Signup and view all the answers

    What is a potential issue caused by functional side effects?

    <p>They can alter operands unexpectedly.</p> Signup and view all the answers

    In languages without functional side effects, two-way parameters are allowed.

    <p>False</p> Signup and view all the answers

    What is one advantage of writing a language definition to disallow functional side effects?

    <p>It works to prevent unintended changes to operands.</p> Signup and view all the answers

    Match the expressions with their explanation:

    <p>average = (count == 0)? 0 : sum / count = Uses a conditional expression a = 10; b = a + fun(a); = Demonstrates functional side effects Fixed operand evaluation order = Limits compiler optimizations Left to right associativity = Default rule for most operators</p> Signup and view all the answers

    Study Notes

    Chapter 6: Expressions and Assignment Statements

    • Expressions are the fundamental means of specifying computations in a programming language.
    • Understanding expression evaluation involves knowing the order of operators and operand evaluation.
    • Imperative languages primarily use assignment statements.
    • Arithmetic expressions consist of operators, operands, parentheses, and function calls.

    Chapter 5 Topics

    • The topics for chapter 5 involve expressions and assignment statements.
    • This chapter includes introduction to expressions, arithmetic expressions, overloaded operators, type conversions, relational and Boolean expressions, short-circuit evaluation, assignment statements, and mixed-mode assignment.

    Introduction

    • Expressions are the essential tools for defining computations within a programming language.
    • To grasp expression evaluation, understanding operator and operand evaluation order is essential.
    • Assignment statements are crucial for imperative languages as they dominate programming.

    Arithmetic Expressions

    • Arithmetic evaluation was a driving force behind the creation of the very first programming languages.
    • Arithmetic expressions in programming comprise operators, operands, parentheses, and function calls.

    Arithmetic Expressions: Design Issues

    • The design of arithmetic expressions includes operator precedence, operator associativity rules, operand evaluation order, operand evaluation side effects, operator overloading, and mode mixing.

    Arithmetic Expressions: Operators

    • A unary operator has one operand.
    • A binary operator has two operands.
    • A ternary operator has three operands.

    Arithmetic Expressions: Operator Precedence Rules

    • Operator precedence rules dictate the order in which adjacent operators with differing precedence levels are evaluated.
    • Typical precedence levels include parentheses, unary operators, exponentiation (if supported), multiplication/division, and addition/subtraction.

    Arithmetic Expressions: Operator Associativity Rule

    • Operator associativity rules define the order in which adjacent operators of the same precedence are executed.
    • Typical associativity is left-to-right, except for exponentiation, which is usually right-to-left.

    Arithmetic Expressions: Conditional Expressions

    • C-based languages use conditional expressions, like average = (count == 0) ? 0 : sum / count to represent conditional operations.
    • This expression checks if the count is zero ; if it is, the average is set to zero else it computes the sum/count

    Arithmetic Expressions: Operand Evaluation Order

    • Variables fetch their values directly from memory.
    • Constant values may be directly available or fetched.
    • Parenthesized expressions are evaluated first (precedence over other sub-expressions), followed by evaluating all their operands and operators.

    Arithmetic Expressions: Potentials for Side Effects

    • Functional side effects happen when a function changes a two-way parameter or a non-local variable making code potentially unpredictable.

    Functional Side Effects

    • Addressing the issues of side effects involves two main approaches controlling side effects within function definitions.
    • Controlling parameter passing in function definitions can reduce issues.
    • Compilers can also be designed to eliminate issues related to operand evaluation orders.

    Overloaded Operators

    • Overloading operators signifies using a single operator symbol for multiple operations.
    • This can be helpful but potentially create problems with compiler error detection and readability, especially when operators have different meanings.

    Overloaded Operators (continued)

    • Programs can implement different meanings for overloaded operators.
    • This may, however, make the program less readable and less reliable.
    • User-defined operators can sometimes result in unintended behavior.

    Type Conversions

    • Narrowing conversions: When a conversion loses some of the possible values of the original data type (e.g., float to int)
    • Widening conversions: When a conversion expands the possible values of the original type in the new data type (e.g., int to float).

    Type Conversions: Mixed Mode

    • A mixed-mode expression mixes different types.
    • Coercions are implicit type conversions from one type to another which are commonly used in programming languages.
    • An added concern is that implicit conversions lower the ability of a compiler to detect some potential type errors.
    • In many languages, numeric types are implicitly converted using widening conversion to fit the intended computation.

    Explicit Type Conversions

    • Explicit type conversions (casting) are used in C-based languages to explicitly change the data type.

    Type Conversions: Errors in Expressions

    • Inherent limitations of arithmetic, like division by zero, or overflow issues.
    • These issues are usually silently handled by the runtime environment.

    Relational and Boolean Expressions

    • Relational expressions utilize relational operators on operands of different types.
    • The outcome of such comparisons is typically represented as Boolean values.
    • Operator symbols for relational comparisons may vary between languages, though they generally mean the same thing!

    Relational and Boolean Expressions: No Boolean Type in C

    • C does not have a distinct Boolean type, using integers (0 for false, non-zero for true) instead.
    • Relational expressions like a<b<c sometimes yield unexpected results in C due to the lack of boolean type or short-circuit evaluation, the way operators are applied one at a time.

    Relational and Boolean Expressions: Operator Precedence

    • The relative precedence of operators, especially those that take on similar roles and overlap in languages like C, needs to be considered.

    Short Circuit Evaluation

    • Short-circuit evaluation is a method of evaluating expressions where further evaluation is unnecessary, potentially saving computational resources, once sufficient information is gathered to know the result.

    Short Circuit Evaluation (continued)

    • The evaluation order in situations where short circuiting is possible is important; the outcome could be different and potentially lead to errors like segmentation faults or incorrect results.

    Assignment Statements

    • Assignment statements use a special syntax which uses assignment operators to set a variable value to a given expression that has a value.
    • Examples of such operators include the simple equals sign (=) and the compounded-assignment operator (+= , -=, etc).

    Assignment Statements: Conditional Targets

    • Certain languages offer conditional assignments, enabling short forms for conditional statements and assignment.

    Assignment Statements: Compound Assignment Operators

    • Compound assignment operators are shorthand notations adopted from other languages to shorten assignment operations when using previously computed values for further operations.

    Assignment Statements: Unary Assignment Operators

    • Certain languages allow combined assignment operations, like those including increment or decrement operations as part of the assignment.

    Assignment as an Expression

    • Assignment statements produce a result, which can also be used as part of larger expressions and larger programs.

    Mixed-Mode Assignment

    • Mixed-mode assignment can occur when different data types are involved in an assignment statement, and how these are handled vary between programming languages.

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    Explore the concepts of expressions and assignment statements in this quiz on Chapter 6. You'll learn about the evaluation of expressions, operator precedence, and the role of assignment statements in imperative programming. Dive into arithmetic expressions and their components for a thorough understanding.

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