CS31-2

CS31-2 - CS 31: Introduction To CS I Topic 2: Flow of...

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Unformatted text preview: CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-1 CS 31 : Introduction to Computer Science I Topic 2 Flow of Control CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-2 Flow of Control Boolean Expressions Are also called conditional expressions Use logical operands and operators Similar to arithmetic expressions Evaluate to true or false Used for selection CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-3 Flow of Control Logical Operators Arithmetic comparison ==, !=, <, >, <=, >= NOTE: == Logical combination !, &&, | | CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-4 Flow of Control Arithmetic Comparison Ops Compare two arithmetic values May be signed or unsigned Result is true or false Examples: 25 <= 40 true 59.374 == 95.81 false CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-5 Flow of Control Logical Combination Ops Unary: ! Not Binary: && And | | Or CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-6 Flow of Control Logical Operators: ! (Not) Unary: Opposite of value !true = false !false = true CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-7 Flow of Control Logical Operators: && (And) Binary: True only if both operands true false && false= false false && true = false true && false = false true && true = true CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-8 Flow of Control Logical Operators: | | (Or) Binary: True only if either operand is true false | | false = false false | | true = true true | | false = true true | | true = true CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-9 Flow of Control Precedence Hierarchy of operators Determines evaluation order without ( ) 18 levels in C++ (Depending on author) Use parentheses to override Use parentheses for clarity CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-10 Flow of Control Precedence Levels (Partial) Postfix increment and decrement Prefix increment and decrement, Unary + and -, Not (!) Multiplicative operators (*, /, %) Additive operators (+, -) I/O operators (<<, >>) Magnitude comparison (<, >, <=, >=) Equality comparison (==, !=) And (&&) Or (| |) Assignment (=) CS 31: Introduction To CS I Topic 2: Flow of Control 1/2009 John A. Rohr All Rights Reserved JAR 2-11 Flow of Control Short-Circuit Evaluation Used for && and | | operators May not evaluate second operand Evaluated only if needed Examples: false && anything false true | | anything true CS 31:...
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CS31-2 - CS 31: Introduction To CS I Topic 2: Flow of...

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