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06a-Expressions

# 06a-Expressions - < “less than”>= “greater than...

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Arithmetic Expressions • Operations on numerical types • Operations: + “addition” - “subtraction” ultiplication” * “multiplication” / “division” (different for int vs. double ) % “remainder” • Precedence (in order): () highest * , / , % + , - lowest Operators in same precedence category evaluated left to right

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Type Casting • Treat one type as another for one operation int x = 3; double y; y = x / 2; // y = 1.0 y = (double)x / 2; y = 5.9; x = (int)y; x = 7; y = x; // fine: y = 7.0 x = y; // error // y = 1.5 // x = 5
Expression Short-hands int x = 3; x = x + 1; x += 1; x++; x = x + 5; x += 5; x = x – 1; x -= 1; x--; x = x * 3; x *= 3; x = x / 2; x /= 2;

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Boolean Expressions • Boolean expression is just a test for a condition • Essentially, evaluates to true or false • Value comparisons: == “equals” (note: not single = ) != “not equals” (cannot say <> ) > “greater than”

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Unformatted text preview: < “less than” >= “greater than or equal to” <= “less than or equal to” More Boolean Expressions • Boolean comparisons (in order of precedence): ! “not” !p if p is true, then !p is false, and vice versa && “and” && q nly true if d e both true p && q only true if p and q are both true || “or” p || q true if p or q (or both) are true boolean p = (x != 1) || (x != 2); p is always true , you really want: boolean p = (x != 1) && (x != 2); Short Circuit Evaluation • Stop evaluating boolean expression as soon as we know the answer • Consider: p = (5 > 3) || (4 <= 2); The test (4 <= 2) is not performed! • Example of useful case: p = (x != 0) && ((y / x) == 0); Avoid division by 0, since ((y / x) == 0) is not performed...
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06a-Expressions - < “less than”>= “greater than...

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