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Relational Operators

Relational Operators. Operator Meaning < Less than > Greater than == Equal to <= Less than or equal to >= Greater than or equal to != Not equal to These are binary operators There must be expressions on either side of the operator

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Relational Operators

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  1. Relational Operators Operator Meaning < Less than > Greater than == Equal to <= Less than or equal to >= Greater than or equal to != Not equal to • These are binary operators • There must be expressions on either side of the operator • Those expressions should evaluate to comparable types. The comparisons will evaluate to true (1) or false (0) • Caution • The two-character relational operators must appear exactly as written above, with the two characters in the proper order and without intervening spaces. • Don’t confuse the assignment operator ( = ) with the relational operator ( == ).

  2. Relational ExpressionsNumeric Expression Meaning Value 4 <= 5 4 less than or equal to 5 true(1) 4 != 4 4 not equal to 4 false(0) 4.0 == 4 real 4.0 equals integer 4 true(1) 4.0 >= 4.0 4.0 greater than or true(1) equal to 4.0 4.0 > 5.0 4.0 greater than 5.0 false(0)

  3. Relational ExpressionsASCII Characters Expression Meaning Value ‘B’ > ‘A’ ‘B’ greater than ‘A’ true(1) ‘g’ < ‘h’ ‘g’ less than ‘h’ true (1) ‘1’ < ‘2’ ‘1’ less than ‘2’ true(1) ‘B’ == ‘b’ ‘B’ equal to ‘b’ false(0) ‘B’ != ‘b’ ‘B’ not equal to ‘b’ true(1) ‘B’ > ‘a’ ‘B’ greater than ‘a’ false(0) ‘B’ > ‘1’ ‘B’ greater than ‘1’ true(1) ‘?’ > ‘!’ ‘?’ greater than ‘!’ true(1)

  4. Logical Operators • The three logical operators allow for creating more complex comparisons. Operator Meaning Type of operator ! Not unary && and binary || or binary

  5. Logical Truth Tables • Semantics of boolean expressions can be described by truth tables (where p and q represent boolean expressions) p !p NOT truth tables true false false true p q p && qAND truth table true true true true false false false true false false false false p q p || q _OR truth table true true true true false true false true true false false false

  6. Understanding Boolean Logic • Suppose that char ans = ‘Y’; int sum = 23; int index = 17; double r = 7.5; int done = true; • Evaluate (ans == ‘Y’) && (index != 0) ______ !(ans < ‘z’) ______ (sum == 45) || (index < r) ______ ( !done) && (index < 30) ______ done && (sum > 21) ______ (r <= r) || (!done) ______ (sum <= 40) || done && !(done) ______

  7. Operator Precedence Operator Precedence Function calls highest ! + - & (Unary operators) * / % + - < <= >= > == != && || = lowest • Note: You may use parentheses to change the order of evaluation.

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