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UVa-Wise COSC 181 - Foundations of Computer Programming

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Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24COSC 181 – Foundations of Computer ProgrammingClass 154.11 Assignment OperatorsAssignment expression abbreviationsAddition assignment operatorExample•c = c + 3; abbreviates to c += 3;Statements of the formvariable = variable operator expression;can be rewritten asvariable operator= expression;Other assignment operators•d -= 4 (d = d - 4)•e *= 5 (e = e * 5)•f /= 3 (f = f / 3)•g %= 9 (g = g % 9)Fig. 4.19 | Arithmetic assignment operators. AssignmentoperatorSampleexpressionExplanation AssignsAssume: int c = 3, d = 5, e = 4, f = 6, g = 12; + = c + = 7 c = c + 7 10 to c -= d -= 4 d = d - 4 1 to d *= e *= 5 e = e * 5 20 to e /= f /= 3 f = f / 3 2 to f % = g % = 9 g = g % 9 3 to g4.12 Increment and Decrement OperatorsIncrement operator ++ Increments variable by oneExample•c++Decrement operator -- Decrement variable by oneExample•c--4.12 Increment and Decrement Operators (Cont.)PreincrementWhen the operator is used before the variable (++c or --c)Variable is changed, then the expression it is in is evaluated using the new valuePostincrementWhen the operator is used after the variable (c++ or c--)Expression the variable is in executes using the old value, then the variable is changedFig. 4.20 | Increment and decrement operators. Operator CalledSampleexpressionExplanation + + preincrement+ + a Increment a by 1, then use the new value ofa in the expression in which a resides. + + postincrementa+ +Use the current value of a in the expressionin which a resides, then increment a by 1. -- predecrement--b Decrement b by 1, then use the new valueof b in the expression in which b resides. -- postdecrementb --Use the current value of b in the expressionin which b resides, then decrement b by 1.Good Programming Practice 4.8 Unlike binary operators, the unary increment and decrement operators should be placed next to their operands, with no intervening spaces.1 // Fig. 4.21: f ig04_21.cpp2 / / Preinc rement ing and post inc rement ing.3 #inc lude < iostream >4 us ing std::cout;5 us ing std::endl;67 int m ain()8 {9 int c;1011 / / demonstrate post increment12 c = 5; // assign 5 to c13 cout < < c < < endl; // print 514 cout < < c+ + < < endl; // print 5 then postincrem ent15 cout < < c < < endl; // print 6 1617 cout < < endl; // skip a line1819 // dem onstrate preincrem ent20 c = 5; // assign 5 to c 21 cout < < c < < endl; // print 5 22 cout < < + + c < < endl; // preincrem ent then print 623 cout < < c < < endl; // print 624 return 0; // indicate successful term ination25 } // end main556566Outlinefig04_21.cpp (1 of 1)Postincrementing the c variablePreincrementing the c variable4.12 Increment and Decrement Operators (Cont.)If c = 5, then •cout << ++c; •c is changed to 6Then prints out 6•cout << c++; Prints out 5 (cout is executed before the increment) •c then becomes 64.12 Increment and Decrement Operators (Cont.)When variable is not in an expressionPreincrementing and postincrementing have same effectExample• ++c; cout << c;and c++; cout << c;are the sameCommon Programming Error 4.14 4Attempting to use the increment or decrement operator on an expression other than a modifiable variable name or reference, e.g., writing ++(x + 1), is a syntax error.Fig. 4.22 | Operator precedence for the operators encountered so far in the text. Operators Associativity Type () left to right parentheses + + -- static_cast< type > () left to right unary (postfix) + + -- + - right to left unary (prefix) * / % left to right multiplicative + - left to right additive < < > > left to right insertion/extraction < < = > > = left to right relational = = !=left to right equality ?: right to left conditional = + = -= *= /= % =right to left assignment13Chapter 5Topics coveredReview of the essentials of counter-controlled repetition.Introduction to the for and do…while repetition statements.Introduction to the switch selection statement.The use of the break and continue program control statements to alter the flow of control.The use of the logical operators to form complex conditional expressions in control statements.Avoiding the consequences of confusing the equality and assignment operators.145.2 Essentials of Counter-Controlled RepetitionCounter-controlled repetition requires:Name of a control variable (loop counter)Initial value of the control variableLoop-continuation condition that tests for the final value of the control variableIncrement/decrement of control variable at each iteration151 // Fig. 5.1: f ig05_01.cpp2 / / Counter - contro l led repet it io n.3 #include < iostream >4 us ing std::cout;5 us ing std::endl;67 int m ain()8 {9 int counter = 1; // declare and initialize control variable1011 while ( counter < = 10 ) // loop-continuation condition12 { 13 cout < < counter < < " ";14 counter+ + ; // increm ent control variable by 115 } // end w hile 1617 cout < < endl; // output a new line18 return 0; // successful term ination19 } // end main1 2 3 4 5 6 7 8 9 10Outlinefig05_01.cpp (1 of 1)Control-variable name is counter with variable initial value 1Condition tests for counter’s final value Increment the value in counter16Common Programming Error 5.1 Floating-point values are approximate, so controlling counting loops with floating-point variables can result in imprecise counter values and inaccurate tests for termination. Control counting loops with integer values.17Good Programming Practice 5.2 Too many levels of nesting can make a program difficult to understand. As a rule, try to avoid using more than three levels of indentation.18Good Programming Practice 5.3 Vertical spacing above and below control statements and indentation of the bodies of control statements within the control statement headers give programs a two-dimensional appearance that greatly improves readability.195.3 for Repetition Statementfor repetition statementSpecifies counter-controlled repetition details in a single line of code201 // Fig. 5.2: f ig05_02.cpp2 / /


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