L05_selection-1

# L05_selection-1 - Making Decisions Making Decisions •...

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Unformatted text preview: Making Decisions Making Decisions • Relational and Logical Operators and Expressions • Control Structures • if and if-else statements EECS 183: University of Michigan Lecture 05 Mary Lou Dorf • Nested if Where we are Headed Where we are Headed – decision making decision making int minimum(int x, int y) { int min; if ( x > y ) { min = y; x > y true false EECS 183: University of Michigan Lecture 05 Mary Lou Dorf } else { min = x; } return min; } min = y; min = x; return min A Note about A Note about true true and and false false • use bool type for variables with values – true or false EECS 183: University of Michigan Lecture 05 Mary Lou Dorf • in C++, when expressions are evaluated, – zero value is considered false, – any non-zero value is considered true Relational & Logical Operators Relational & Logical Operators • Relational Operators < <= > >= == != • Logical Operators EECS 183: University of Michigan Lecture 05 Mary Lou Dorf && ( and ) || ( or ) ! ( not ) • used to compare values Relational Operators Relational Operators • all are binary – two operands • x > y is x greater than y? • x < y is x less than y? • x >= y is x greater than or equal to y? • x <= y is x less than or equal to y? == y x equal to y? EECS 183: University of Michigan Lecture 05 Mary Lou Dorf • x == y is x equal to y? • x != y is x not equal to y? • all evaluate to either true or false assume assume x is 10 and y is 7 x is 10 and y is 7 • x < y • x > y • x >= y EECS 183: University of Michigan Lecture 05 Mary Lou Dorf • x <= y • y != x bool undergrad = true; int age = 20; char gender = 'F'; EXPR___ ndergrad Example Relational Expressions Example Relational Expressions VALUE ue EECS 183: University of Michigan Lecture 05 Mary Lou Dorf • undergrad • age <= 25 • gender == 'M' • gender = 'M' • (age % 2) == 0 true true false true ('M') – (Also: gender ← ‘M’) true OPERATOR ASSOCIATIVITY HIGH ( ) left to right ! + - cast unary; right to left * / % left to right Precedence Rules Precedence Rules Recap Recap EECS 183: University of Michigan Lecture 05 Mary Lou Dorf + - left to right < <= > >= left to right == != left to right = right to left LOW swap out for swap out for L05_example 1.cpp L05_example 1.cpp EECS 183: University of Michigan Lecture 05 Mary Lou Dorf solve solve • 1) given x = 5, y = 6, z = 8 – what is the value of x == 5 (2 + x) != y • Is the following correct? EECS 183: University of Michigan Lecture 05 Mary Lou Dorf – x <= y is the same as y > x • If it is true that x > y and it is also true that x < z, does that mean y < z is true? SEQUENCE SEQUENCE tatement tatement tatement . . . EECS 183: University of Michigan Lecture 05 Mary Lou Dorf Statement Statement Statement SELECTION(branch) SELECTION(branch) IF Condition THEN Statement1 ELSE Statement2 EECS 183: University of Michigan Lecture 05 Mary Lou Dorf Statement1 Statement Statement2 Condition . . . if statement ("if if statement ("if-then")...
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L05_selection-1 - Making Decisions Making Decisions •...

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