Expressions

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1 Arithmetic Expressions • Operations on numerical types • Operations: + “addition” - “subtraction” * “multiplication” / “division” (different for int vs. double ) % “remainder” • Precedence (in order): () highest * , / , % + , - lowest Operators in same precedence category evaluated left to right Type Casting • Treat one type as another for one operation int x = 3; double y; y = x / 2; y = (double)x / 2; y = 5.9; x = (int)y; x = 7; y = x; // fine: y = 7.0 x = y; // error // y = 1.0 // 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; 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
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Unformatted text preview: <> ) > greater than < 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 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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