C++ Iterative Constructs

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Presentation transcript:

C++ Iterative Constructs Three constructs while statement for statement do-while statement

While Syntax

While Semantics

Computing an Average int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl;

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl;

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl;

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum value --

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum value 1

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 1 value 1

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 1 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 1 value 1

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 1 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 1 value 1

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 1 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 1 value --

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 1 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 1 value 5

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 1 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 6 1 value 5

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 2 1 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 6 value 5

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 2 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 6 6 value 5

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 2 2 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 6 value --

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 2 2 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 6 value 3

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 2 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 9 6 value 3

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 3 2 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 9 value 3

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 3 3 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 9 value 3

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 3 3 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 9 value --

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 3 3 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 9 value 1

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 3 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 10 9 value 1

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 4 3 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 10 value 1

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 4 3 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 10 value 1

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 4 3 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 10 average 2.5

Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4 numberProcessed 4 3 int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; sum 10 average 2.5

Stays in stream until extracted Suppose input contains: 1 5 3 1 6 Execution Trace Stays in stream until extracted int listSize = 4; int numberProcessed = 0; double sum = 0; while (numberProcessed < listSize) { double value; cin >> value; sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl;

Power of Two Table const int TableSize = 20; int i = 0; long Entry = 1; cout << "i" << "\t\t" << "2 ** i" << endl; while (i < TableSize) { cout << i << "\t\t" << Entry << endl; Entry = 2 * Entry; ++i; }

Better Way of Averaging The value of the input operation corresponds to true only if a successful extraction was made int numberProcessed = 0; double sum = 0; double value; while ( cin >> value ) { sum += value; ++numberProcessed; } double average = sum / numberProcessed ; cout << "Average: " << average << endl; What if list is empty?

Even Better Way of Averaging int numberProcessed = 0; double sum = 0; double value; while ( cin >> value ) { sum += value; ++numberProcessed; } if ( numberProcessed > 0 ) { double average = sum / numberProcessed ; cout << "Average: " << average << endl; else { cout << "No list to average" << endl;

The For Statement Syntax for (ForInit ; ForExpression; PostExpression) Action Example for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }

Execution Trace i for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl;

Execution Trace i for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl;

Execution Trace i for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0

Execution Trace i for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0

Execution Trace i 1 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0

Execution Trace i 1 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl;

Execution Trace i 1 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0 i is 1

Execution Trace i 1 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0 i is 1

Execution Trace i 2 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0 i is 1

Execution Trace i 2 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0 i is 1

Execution Trace i 2 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0 i is 1 i is 2

Execution Trace i 2 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0 i is 1 i is 2

Execution Trace i 3 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0 i is 1 i is 2

Execution Trace i 3 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0 i is 1 i is 2

Execution Trace i 3 for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; } cout << "all done" << endl; i is 0 i is 1 i is 2 all done

Table Revisiting const int TableSize = 20; long Entry = 1; cout << "i" << "\t\t" << "2**i" << endl; for (int i = 0; i <= TableSize; ++i) { cout << i << "\t\t" << Entry << endl; Entry *= 2; }

Table Revisiting const int TableSize = 20; long Entry = 1; cout << "i" << "\t\t" << "2**i" << endl; for (int i = 0; i < TableSize; ++i) { cout << i << "\t\t" << Entry << endl; Entry = 2 * Entry; } cout << "i is" << i << endl; // illegal The scope of i is limited to the loop!

int Counter1 = 0; int Counter2 = 0; int Counter3 = 0; int Counter4 = 0; int Counter5 = 0; ++Counter1; for (int i = 1; i <= 10; ++i) { ++Counter2; for (int j = 1; j <= 20; ++j) { ++Counter3; } ++Counter4; } ++Counter5; cout << Counter1 << " " << Counter2 << " " << Counter3 << " " << Counter4 << " " << Counter5 << endl;

For Into While Observation The for statement is equivalent to { ForInit; while (ForExpression) { Action; PostExpression; }