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开始学习
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An expression is a combination of values, variables, operators and function calls. Expressions perform operations on data and move data around
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how many oprands does a unary operator have? 开始学习
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1 eg E.g., the “minus” operator. - b where “-” is operator, and b operand
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how many oprands does a binary operator have? 开始学习
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[1] A binary operator has two operands E.g., +, -, *, /... [2] In most languages, binary operators are infix, which means they appear between their operands [3] There are also operators that are prefix, i.e., they precede their operands.
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What are the typical rules of precedence 开始学习
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[1] Parentheses: “(” “)” [2] Unary operators “++”, “--” [3] Unary operators “+” “-” [4] Binary operators “*”, “/” [5] Binary operators: “+” “-”
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explain Operator Associativity Rules 开始学习
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The operator associativity rules for expression evaluation define the order in which “adjacent” operators of the same precedence levels are evaluated
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when does and expression have side effects 开始学习
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We say an expression has a side effect if, in addition to return a value, it also modifies variables or causes something else to happen.
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what is the genral syntax of the Assignment operator 开始学习
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<target_var> <assign_operator> <expression>
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what are Compound Assignment Operators 开始学习
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[1] Compound means combining assignment with arithmetic operators. [2] It is a shorthand method of specifying a commonly needed form of assignment. [3] eg a = a + b writen as a += b
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what is a Unary Assignment Operators 开始学习
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[1] Unary assignment operators in C-based languages combine increment and decrement operations with assignment eg count++ (count incremented by 1, i.e., count = count+1)
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开始学习
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Cast refers to type conversion that is explicitly requested by the programmer.
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开始学习
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[1] Coercion is an implicit type conversion that is initiated by the compiler. [2] The compiler checks the type compatibility of the assignment and changes the type of right side of the assignment.
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what is a widening conversion 开始学习
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A widening conversion is one in which an object is converted to a type that allow any possible value of the original data (i.e., converting to a type takes a larger memory space)
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what is A narrowing conversion 开始学习
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[1] usually done explicitly as a request from the programmers [3]e. g Java can convert int to short one needs to process the int value in a method design to work with short values. [4] The conversion is not safe (overflow may happen).
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what are Relational operators 开始学习
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[1] Relational operator is a binary operator that compare the values of its operands and the result is a Boolean value True or False. [2] eg “Not Equal” operator could be one of these:!=,/=, ~=,. NE. or <>.
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what is Short Circuit Evaluation 开始学习
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[1] expression eval' where the result is determined w/out eval'ng all of the operands and/or operators [2] (a>=0)&&(b<10) if (a<0), because (False && (b<0))is False for all value of b. Therefore, there is no need to evaluate (b<0)
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