Download presentation

Presentation is loading. Please wait.

Published byLeah Reed Modified over 4 years ago

1
Lecture 5 -- 1Computer Science I - Martin Hardwick Arithmetic Expressions With Integers rOperators:result is always an integer SymbolNameExampleValue (x = 10, y=3) +addition x + y13 –subtractionx – y 7 *multiplicationx * y30 /quotient x / y 3 %remainderx % y 1 –unary minus –x-10 +unary plus +x 10 rYou can string the operators together to build longer expressions. l use parentheses to specify order of operations l precedence (after sub-expressions in parentheses) –first:unary plus and minus from right to left –second: *, / and % from left to right –third: + and – from left to right

2
Lecture 5 -- 2Computer Science I - Martin Hardwick Arithmetic Expression Examples 12 + 2 * 5 - 8 / 3 + 6 10 2 22 20 26 -2 * 3 * (4 + 5) % 10 + -3 -3 -2 9 -6 -54 -4 -7

3
Lecture 5 -- 3Computer Science I - Martin Hardwick Arithmetic Exprs With Doubles rArithmetic expressions with real numbers (numbers with decimal points) work the same way as with integers, with a few exceptions: l there is no remainder operator (%) l the / operator means divide, computing the answer to many decimal places l the result is a real value rather than an integer value rImportant: Real values are approximate and may contain errors in the last few digits. l about 7 digits of accuracy for type float (one word) l about 14 digits of accuracy for type double (two words) l so programmers today nearly always use doubles rReal values are often represented using scientific notation. l Example: 1.857409 x 10 2

4
Lecture 5 -- 4Computer Science I - Martin Hardwick Mixed Mode Arithmetic Expressions rArithmetic expressions both integers and doubles can get tricky. l if both operands are integers, integer arithmetic is used l if either operand is a double, double arithmetic is used –an integer operand is converted to double for the operation rExample:assume a and b are int variables assume x and y are double variables (a * b + (a - b) * x) / (a + b) int double

5
Lecture 5 -- 5Computer Science I - Martin Hardwick Roots Of A Quadratic Equation //Find roots of Ax 2 + Bx + C = 0 #include using namespace std; int main () { doubleA, B, C, x1, x2, sqrtOfDiscriminant; //get three inputs cout << "Enter the value for A: "; cin >> A; cout << "Enter the value for B: "; cin >> B; cout << "Enter the value for C: "; cin >> C; rThe roots of a quadratic equation Ax 2 + Bx + C = 0 are: rTo compute the roots, we need to ask the user for the values of A, B and C. l the cin statement does this l prompt user to enter data rNote that you can declare more than one variable per line. rThe C++ math library (cmath) contains a square root function. -B ± B 2 - 4AC 2A

6
Lecture 5 -- 6Computer Science I - Martin Hardwick Roots Of A Quadratic Equation (continued) //compute the two solutions sqrtOfDiscriminant = sqrt(B*B- 4*A*C); x1 = (-B+sqrtOfDiscriminant) / (2*A); x2 = (-B-sqrtOfDiscriminant) / (2*A); //display the results cout << "First solution: " << x1 << endl; cout << "Second solution: " << x2 << endl; return 0; } rsqrt is the name of the square root function in the library resource. rWhen a variable appears after the << operator in a cout statement, the value of the variable is displayed. rNote that the parentheses in the computation of x1 and x2 are needed to produce the correct result.

7
Lecture 5 -- 7Computer Science I - Martin Hardwick Common errors rNot initializing a variable before it is used // Author: Martin Hardwick #include using namespace std; int main () { int a, b; a = b + 6; return 0; }

8
Lecture 5 -- 8Computer Science I - Martin Hardwick Increment and Decrement operators rThese operators are an easy way to increase (++) or decrease (--) a value by one. rUsed a lot in For loops int main () { int x, y; x = 5; y = x++; cout << x << y << endl; return 0; } int main () { int x, y; x = 5; y = ++x; cout << x << y << endl; return 0; } Prints 6, 5Prints 6, 6 Post-incrementPre-increment

9
Lecture 5 -- 9Computer Science I - Martin Hardwick Conditional Execution -- Quadratic Formula //Find roots of Ax 2 + Bx + C = 0 #include using namespace std; int main () { doubleA, B, C, x1, x2; doublesqrtOfDiscriminant; //get three inputs cout << "Enter the value for A: "; cin >> A; cout << "Enter the value for B: "; cin >> B; cout << "Enter the value for C: "; cin >> C; rA quadratic equation may have only one root. l the quadratic formula computes this root twice l only want to display the root once rOur program needs some way to check that the two roots are different before displaying both. l this is the purpose of the IF statement in C++ rIF statements are also useful for verifying that the user entered correct data as will be seen in future classes.

10
Lecture 5 -- 10Computer Science I - Martin Hardwick Quadratic Formula (continue) rWe need to create a special case that displays the second root only when it is different from the first. rAn IF statement specifies: l conditions that define the special case l sequence of statements to execute for the special case r!= means not equal rthe braces (i.e., { }) define a block of statements to execute. //compute the two solutions sqrtOfDiscriminant = sqrt( B*B - 4*A*C ); x1 = (-B+sqrtOfDiscriminant)/(2*A); x2 = (-B-sqrtOfDiscriminant)/(2*A); //display the first root cout << "First solution: " << x1 << endl; //display the second root if different if (x1 != x2) { cout << "Second solution: " << x2 << endl; } return 0; }

11
Lecture 5 -- 11Computer Science I - Martin Hardwick IF Statements rSyntax:if ( condition ) { statement1; statement 2;... } rThe condition is any valid logical expression with relational operators and logical operators (more on this later). rThe statements inside the IF statement can be any valid C++ statements including other IF statements. rMeaning: condition statement1; statement2;... true false Handle one special case

12
Lecture 5 -- 12Computer Science I - Martin Hardwick The Condition In An IF Statement rThe condition in an IF statement is any valid logical expression composed of relational and logical operators. rRelational operators: operatordescriptionexampleresult x = 10, y=2

13
Lecture 5 -- 13Computer Science I - Martin Hardwick The Condition In An IF Statement (continued) rLogical operators: ABorandnot A || BA && B!A falsefalsefalsefalsetrue falsetruetruefalsetrue truefalsetruefalsefalse truetruetruetruefalse rPrecedence for a logical expression: l expressions in parentheses l arithmetic expressions l relational operators l and l or in order from left to right unless otherwise specified

14
Lecture 5 -- 14Computer Science I - Martin Hardwick Example Conditions ( x = 10, y = 20) (x+1 > 0) || (y == x) && (x+y < 25)!x + 1 > 0 || y == x && x + y < 25 (11 > 0) TRUE (20 = = 10) FALSE (30 < 25) FALSE FALSE && FALSE FALSE TRUE || FALSE TRUE (11 > 0) (20 = = 10) (30 < 25) TRUE FALSE

Similar presentations

OK

Lecture 5: Expressions and Interactivity Professor: Dr. Miguel Alonso Jr. Fall 2008 CGS2423/COP1220.

Lecture 5: Expressions and Interactivity Professor: Dr. Miguel Alonso Jr. Fall 2008 CGS2423/COP1220.

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on microcontroller based home security system Ppt on children's day in india Ppt on chemical reactions and equations class 10 free download Ppt on greenhouse effect and global warming Ppt on nature of matter for class 6 Ppt on word association tests Powerpoint ppt on spinal injuries Hrm ppt on recruitment Ppt on alternative fuels for i.c engine Ppt on supply chain management of nokia pc