Section 1
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What does a widening conversion do?
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Mar 1, 2020
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Section 1
(50 cards)
What does a widening conversion do?
Converts a value to a type that can include at least approximations of all of the values of the original type
What is the name of an operator that has three operators?
Ternary
What do Boolean operators take and produce?
Boolean operands and Boolean values
What arithmetic operations are only approximations of their mathematical counterparts?
Floating-point
When does a program have the property of referential transparency?
if any two expressions in the program that have the same value can be substituted for one another anywhere in the program, without affecting the action of the program
Arithmetic operators are often used for how many purposes?
More than one
What are the two types of associativity?
Left and right
What is the concept of referential transparency related to?
Functional side effects
Although widening conversions are usually safe, what can they sometimes result in?
Reduced accuracy
Those who would rather include a wide range of coercions are more concerned with what?
The loss in flexibility that results from restrictions
What are the two forms of type conversion?
Widening or narrowing, explicit and implicit
A relational operator is an operator that does what?
Compares the values of its two operands
When is operator overloading acceptable?
When neither readability nor reliability suffer
Where were most of the characteristics of arithmetic expressions in programming languages inherited from?
Mathematics
What are mixed mode expressions?
When an operator can has operands of different types
What is the purpose of an arithmetic expression?
To specify an arithmetic computation
The Boolean operators usually include those for what?
AND, OR, and NOT operations, and sometimes for exclusive OR and equivalence
The operation that determines the truth or falsehood of a relational expression depends on what?
The operand types
What are the fundamental means of specifying computations in a programming language?
Expressions
What are some issues in expression semantics?
Type mismatches, coercions, and short-circuit evaluation
Those against a broad range of coercions are concerned with what?
The reliability problems that can result from such coercions
In all of the common imperative languages, where can the unary minus operator appear in an expression?
Either at the beginning or anywhere inside the expression
What dictates the order of evaluation of its operators?
Operator precedence and associativity rules of a language
When the two operands of an operator are not of the same type and that is legal in the language, what must the compiler do?
The compiler must choose one of them to be coerced and supply the code for that coercion
What is the name of an operator that has a single operand?
Unary
What are two possible solutions to the problem of operand evaluation order and side effects?
First, the language designer could disallow function evaluation from affecting the value of expressions by simply disallowing functional side effects. Second, the language definition could state that operands in expressions are to be evaluated in a particular order and demand that implementors guarantee that order.
How are variables in expressions evaluated?
By fetching their values from memory
What is the operator evaluation order of expressions is dictated by?
The associativity and precedence rules of the language
What is a short-circuit evaluation of an expression?
One in which the result is determined without evaluating all of the operands and/or operators
What is the most important advantage to referentially transparent programs?
That the semantics of such programs is much easier to understand than the semantics of programs that are not referentially transparent
What are the operator precedence rules for expressions are based on?
The hierarchy of operator priorities, as seen by the language designer
What does a narrowing conversion do?
Converts a value to a type that cannot store even approximations of all of the values of the original type
What is the name of an operator that has two operands?
Binary
What is operator overloading?
The multiple use of an operator
The relational operators always have _______ precedence than the arithmetic operators.
Lower
Why are programs written in pure functional languages referentially transparent?
Because they do not have variables
A relational expression has how many operands and operators?
Two operands and one relational operator
If the language requires type checking, either static or dynamic, what errors cannot occur?
Operand type errors
What is it called when when the result of an operation cannot be represented in the memory cell where it must be stored?
Overflow or underflow, depending on whether the result was too large or too small
What is an infix operator?
A descriptor for operators that appear between their operands
What is the purpose of assignment statements?
To cause the side effect of changing the values of variables, or the state, of the program
How can programmers alter the precedence and associativity rules?
By placing parentheses in expressions
When does a a functional side effect occur?
When the function changes either one of its parameters or a global variable
Boolean expressions consist of what?
Boolean variables, Boolean constants, relational expressions, and Boolean operators
The value of a relational expression is what?
Boolean, except when Boolean is not a type included in the language
Floating-point overflow, underflow, and division by zero are examples of what kinds of errors?
Run-time errors, which are sometimes called exceptions
The value of an expression depends at least in part on what?
The order of evaluation of the operators in the expression
The most common error in expressions occurs when what happens?
The result of an operation cannot be represented in the memory cell where it must be stored
What is the essence of the imperative programming languages?
The dominant role of assignment statements
What are type conversions explicitly requested by the programmer are called what?
Explicit conversions, or casts, NOT coercions
Section 2
(3 cards)