The University of Iowa
The College of Liberal Arts and Sciences
Department of Computer Science
Programming Languages and Tools:
CS:3210:0001
Lecture/Lab #7
Programming with C++
Compound assignment, increment/decrement, control flow
Warm-up
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What's the difference between x && y and x & y?
-
What will be the output of the following program?
int main() {
std::cout
<< std::boolalpha
<< !( 2 > 4 )
<< "\n";
}-
What does the x << y expression do?
Compound assignment
x = x + n;
x = x - n;
x = x * n;
x = x / n;
x = x % n;
x = x & n;
x = x | n;
x = x ^ n;
x = x << n;
x = x >> n;x += n;
x -= n;
x *= n;
x /= n;
x %= n;
x &= n;
x |= n;
x ^= n;
x <<= n;
x >>= n;Is there a better way to express these?
Yes!
Increment/decrement
x += 1;
x -= 1;
Is there a better way to express these?
Yes!
++x;
--x;
OR...
x++;
x--;
-
Pre-increment and pre-decrement operators increment or decrement the value of the object and return a reference to the result
-
Post-increment and post-decrement create a copy of the object, increment or decrement the value of the object and return the copy from before the increment or decrement
Control flow overview
if ( <condition> ) <statement> [else <statement>]
do <statement> while ( <condition> )
while ( <condition> ) <statement>
for ( <init-statement>; <condition>; <expression> ) <statement>
switch ( <condition> ) {
( ( case <constant> | default ): <statement> )+
}
If statement
if ( <condition> ) <statement> [else <statement>]
// the product of an integer and
// all the integers before it
int factorial( int n )
{
if ( n == 0 )
return 1;
else
return n * factorial( n - 1 );
}
Conditionally executes the first or the second statement.
Exercise 1
Write a program that asks user for a number and prints "Yay" or "Nay" depending on the condition
-
Open the exercise template
-
Write your code, press Run to test
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When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)
-
Click on the corresponding option in the "Lab7 exercises" poll in #general
while statement
while ( <condition> ) <statement>
// the product of an integer and
// all the integers before it
int factorial( int n )
{
int result = 1;
while ( n > 0 )
{
result = result * n;
n = n - 1;
}
return result;
}
Executes statement repeatedly, until condition becomes false. The condition is tested before each iteration.
do-while loop
int prompt_for_positive()
{
int n = -1;
do
{
std::cout << "Enter a positive number: ";
std::cin >> n;
}
while ( n <= 0 );
return n;
}
do <statement> while ( <condition> )
Executes statement repeatedly, until condition becomes false. The condition is tested after each iteration.
Exercise 2
Write a program that asks user for a positive integer and prints out all the integers between zero and the input
( [0, input) )
-
Open the exercise template
-
Write your code, press Run to test
-
When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)
-
Click on the corresponding option in the "Lab7 exercises" poll in #general
for loop
#include <iostream>
int main()
{
for ( int i = 0; i < 10; ++i )
std::cout << i << " ";
}
Executes init-statement once, then executes statement and expression repeatedly, until the condition becomes false. The condition is tested before each iteration.
for ( <init-statement>; <condition>; <expression> ) <statement>
Exercise 3
-
Open the exercise template
-
Write your code, press Run to test
-
When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)
-
Click on the corresponding option in the "Lab7 exercises" poll in #general
Write a program that asks user for a positive integer and uses `for` loop to print out all the even numbers between zero and the input
switch statement
char c = 0;
std::cin >> c;
switch ( c )
{
case 'y':
case 'Y':
return true;
case 'n':
case 'N':
return false;
default:
return default_;
}
switch ( <condition> ) {
( ( case <constant> | default ): <statement> )+
}
Transfers control to one of the several statements, depending on the value of condition.
Exercise 4
Write a program that asks user to make a selection from three items and uses `switch` statement to print out the selected item
-
Open the exercise template
-
Write your code, press Run to test
-
When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)
-
Click on the corresponding option in the "Lab7 exercises" poll in #general
Programming with C++, Spring 2020, Lecture #7
By Aleksey Gurtovoy
Programming with C++, Spring 2020, Lecture #7
Compound assignment, increment/decrement, control flow
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