Programming in C DaleWeemsHeadington Chapter 3 Arithmetic Expressions

Programming in C++ Dale/Weems/Headington Chapter 3 Arithmetic Expressions, Function Calls, and Output 1

What is an Expression in C++? l An expression is any valid combination of operators and operands. l In C++ each expression has a value. 2

Operators can be binary involving 2 operands 2+3 unary involving 1 operand -3 ternary involving 3 operands later 3

Some C++ Operators Precedence Higher Lower Operator ( ) + * / % + = Description Function call Positive Negative Multiplication Division Modulus (remainder) Addition Subtraction Assignment 4

Precedence l Higher Precedence determines which operator is applied first in an expression having several operators. 5

Associativity l Left to right Associativity means that in an expression having 2 operators with the same priority, the left operator is applied first. l In C++ the binary operators * , / , % , + , - are all left associative. l Expression 9 - 5 - 1 means ( 9 - 5 ) - 1 4 -1 3 6

Evaluate the Expression means 7 * 10 - 5 % 3 * 4 + 9 (7 * 10) - 5 % 3 * 4 + 9 70 - (5 % 3) * 4 + 9 70 - 2 * 4 + 9 70 - ( 2 * 4 ) + 9 70 - 8 + 9 ( 70 - 8 ) + 9 62 + 9 71 7

Parentheses can be used to change the usual order l Parts in ( ) are evaluated first l Evaluate (7 * (10 - 5) % 3) * 4 + 9 l (7 * 5 % 3 ) * 4 ( 35 % 3 ) * 4 2 * 4 8 + 9 + 9 17 8

Assignment Operator Syntax Variable. Name = Expression First, Expression on right is evaluated. Then the resulting value is stored in the memory location of Variable. Name on left. NOTE: An automatic type coercion occurs after evaluation but before the value is stored if the types differ for Expression and Variable. Name 9

What value is stored? float A; float B; A = 8. 5; B = 9. 37; A = B; A 8. 5 A ? B 9. 37 B ? 10

What is stored? float Some. Float; ? Some. Float = 12; // causes implicit type conversion 12. 0 Some. Float 11

What is stored? int Some. Int; ? Some. Int = 4. 8; // causes implicit type conversion 4 Some. Int 12

Type Casting is Explicit Conversion of Type int(4. 8) has value 4 float(5) has value 5. 0 float(7/4) has value 1. 0 float(7) / float(4) has value 1. 75 13

<iostream. h> is header file l for a library that defines 3 objects l an istream object named cin (keyboard) l an ostream object named cout (screen) l an ostream object named cerr (screen) 14

No I/O is built into C++ l Instead, a library provides input stream and output stream Keyboard Screen executing program istream ostream 15

>> is a binary operator >> is called the input or extraction operator >> is left associative EXPRESSION HAS VALUE cin >> Age cin STATEMENT cin >> Age >> Weight ; 16

<< is a binary operator << is called the output or insertion operator << is left associative EXPRESSION cout << Age HAS VALUE cout STATEMENT cout << “You are “ << Age << “ years oldn” ; 17

Some Expressions int Age; EXAMPLE Age = 8 - Age 5+8 5/8 6. 0 / 5. 0 float ( 4 / 8 ) float ( 4 ) / 8 cout << “How old are you? ” cin >> Age cout << Age VALUE 8 -8 13 0 1. 2 0. 0 0. 5 cout cin cout 18

What values are stored? float Lo. Cost; float Hi. Cost; Lo. Cost = 12. 342; Hi. Cost = 12. 348; Lo. Cost = float (int (Lo. Cost * 100. 0 + 0. 5) ) / 100. 0; Hi. Cost = float (int (Hi. Cost * 100. 0 + 0. 5) ) / 100. 0; 19

Values were rounded to 2 decimal places 12. 34 Lo. Cost 12. 35 Hi. Cost 20

Functions l Every C program must have a function called main ( ) l Program execution always begins with function main ( ) l Any other functions are subprograms and must be called. 21

What is in a block? { 0 or more statements here } 22

Function Calls l One function calls another by using the name of the called function together with ( ) containing a parameter list l A function call temporarily transfers control from the calling function to the called function 23

Parts of a Function l Every function has 2 parts int main (void) { heading body block return 0; } 24

What is in a heading? type of returned value name of function says no parameters int main (void) 25

More about functions l It is not considered good practice for the body block of main ( ) to be long. l Function calls are used to do tasks l Every C++ function has a return type l If the return type is not void, the function returns a value to the calling block. 26

Where are functions? located in libraries OR written by programmers 27

HEADER FILE <stdlib. h> FUNCTION EXAMPLE OF CALL VALUE abs(i) abs(-6) 6 fabs(x) fabs(-6. 4) 6. 4 <math. h> pow(x, y) pow(2. 0, 3. 0) 8. 0 <math. h> sqrt(x) sqrt(100. 0) 10. 0 sqrt(x) sqrt(2. 0) 1. 41421 log(x) log(2. 0) . 693147 <math. h> <iomanip. h> setprecision(n) setprecision(3) 28

Write C++ Expressions for 2 The square root of b - 4 ac sqrt ( b * b - 4. 0 * a * c ) The square root of the average of My. Age and Your. Age sqrt ( (My. Age + Your. Age) / 2 ) 29

Manipulators l Manipulators are used only in input and output statements. l endl, setw, and setprecision are manipulators that can be used to control output format. l endl is use to terminate the current output line, and create blank lines in output. 30

Insertion Operator ( << ) l The insertion operator << takes 2 operands. l The left operand is a stream expression, such as cout. l The right operand is an expression of simple type, or a string, or a manipulator. 31

Output Statements SYNTAX (revised) cout << Expr. Or. String. Or. Manipulator. . . ; 32

setprecision(n) l requires #include <iomanip. h> and appears in an expression using insertion operator (<<) l specifies n as the number of places displayed after the decimal point for floating point values l remains in effect until explicitly changed by another call to setprecision 33

What is exact output? #include <iomanip. h> #include <iostream. h> int main ( void) { float my. Number = 123. 4587 ; cout. setf ( ios: : fixed , ios: : floatfield ) ; cout. setf ( ios: : showpoint ) ; // use decimal format // print decimal point cout << “Number is ” << setprecision ( 3 ) << my. Number << endl ; return 0 ; } 34

OUTPUT Number is 123. 459 value is rounded if necessary to be displayed with exactly 3 places after the decimal point 35

setw(n) l requires #include <iomanip. h> and appears in an expression using insertion operator (<<) l affects only the very next item displayed l “set width” specifies n as the number of total columns in which to display a number or string (not char data). Parameter n is called the fieldwidth specification. The number of columns used is expanded if n is too narrow. l is useful to align columns of output 36

What is exact output? #include <iomanip. h> #include <iostream. h> int main ( void) { float my. Number = 123. 4 ; float your. Number = 3. 14159 ; cout. setf ( ios: : fixed , ios: : floatfield ) ; cout. setf ( ios: : showpoint ) ; // use decimal format // print decimal point cout << “Numbers are: ” << setprecision ( 4 ) << endl << setw ( 10 ) << my. Number << endl << setw ( 10 ) << your. Number << endl ; return 0 ; } 37

OUTPUT Numbers are: 123. 4000 3. 1416 each is displayed right-justified and rounded if necessary and each is located in a total of 10 columns with 4 places after the decimal point 38

Using setf( ) l setf( ) is a function associated with output streams. To call this function use this syntax Desired. Output. Stream. setf( Parameter. List ) ; l setf( ) can be used to print the decimal point (even if there are trailing zeros) for floating values that are output, and to specify that the value be printed with a fixed position decimal point (rather than in scientific notation). 39

cout. setf( ) statements l Use the following statements to specify that (for output sent to the cout stream) decimal format (not scientific notation) be used, and that a decimal point be included (even for floating values with 0 as fractional part). cout. setf( ios : : fixed, ios : : floatfield ) ; cout. setf( ios : : showpoint ) ; 40

312. 0 More examples 4. 827 x float x = 312. 0 ; float y = 4. 827 ; cout. setf ( ios: : fixed , ios: : floatfield ) ; cout. setf ( ios: : showpoint ) ; y OUTPUT cout << setprecision ( 2 ) << setw ( 10 ) << x << endl << setw ( 10 ) << y << endl ; ’’’’ 3 1 2. 00 ’’’’’’ 4. 83 cout << setprecision ( 1 ) << setw ( 10 ) << x << endl << setw ( 10 ) << y << endl ; ’’’’’ 3 1 2. 0 ’’’’’’’ 4. 8 cout << setprecision ( 5 ) << setw ( 7 ) << x << endl << setw ( 7 ) << y << endl ; 3 1 2. 00000 4. 82700 41

Program with several functions main( ) function Square( ) function Cube( ) function 42

Value-returning functions #include <iostream. h> int Square ( int ) ; int Cube ( int ) ; // declares these 2 functions int main ( void ) { cout << “The square of 27 is “ << Square (27) << endl ; cout << “The cube of 27 is “ << Cube (27) << endl ; return 0 ; // function call } 43

Rest of Program int Square ( int n ) // header and body here { return n * n ; } int Cube ( int n ) // header and body here { return n * n ; } 44

A void function call stands alone #include <iostream. h> void Display. Message ( int n ) ; // declares function int main(void) { Display. Message( 15 ) ; //function call cout << “Good Bye“ << endl ; return 0 ; } 45

A void function does NOT return a value void Display. Message ( int n ) // header and body here { cout << “I have liked math for “ << n << “ years” << endl ; } 46