Numeric Types, Expressions, and Output

1. Numeric Types, Expressions, and Output Robert Reaves

2. Compound Arithmetic Expressions • Arithmetic expressions can be made up of many constants, variables, operators, and parentheses. • Precedence Level (highest  lowest) • Unary +, Unary - • *, /, % • +, - • (…) are always evaluated first. • Ex. • 10 / 2 * 3 = 15 • 10 % 3 – 4 / 2 = -1 • 5.0 * 2.0 / 4.0 * 2.0 = 5.0 • 5.0 * 2.0 / (4.0 * 2.0) =1.25

3. Type Coercion and Type Casting • Type Coercion is the implicit (automatic) conversion of a value from one data type to another. • Ex. • float someFloat = 12; • Computer inserts extra machine language instructions to convert to 12.0. • Type Casting is the explicit conversion of a value from one data type to another, also called type conversion. • A C++ cast operation consists of a data type name and then, within parentheses, the expression to be converted. • Ex. • float someFloat = float(3 * someInt * 2);

4. Arithmetic Expressions • Possible to mix data types within an expression, this is called mixed type expression or mixed mode expression. • Whenever an integer value and floating-point value are joined by an operator, implicit type coercion occurs: • Integer value is temporarily coerced to a floating-point value • Operation is performed • Result is a floating-point value

5. What is a value-returning function? • A function that returns a single value to its caller and is invoked from within an expression.

6. Void Functions • void myFunc( . . .) { . . } • Notice how it begins with the word void instead of a data type like intor float. • Void Function( (procedure) is a function that does not return a function value to its caller and is invoked as a separate statement. • What do you mean by a separate statement?

7. Formatting Output • What this means is to control how output appears visually on the screen or on a printout. • The C++ standard library supplies many manipulators, but we will look at only five of them: • endl • setw • fixed • showpoint • setprecision

8. Header Files • endl, fixed, and showpoint are including inside the iostreamheader file to perform I/O. • #include <iostream> • setw and setprecision are inside the iomanipheader file. • #include <iomanip>

9. Setw • setwmeans “set width”, it lets us control how many character positions the next data item should occupy when it is output. • Cout << setw(4) << “Hi” << endl; • Output (_ means blank) _ _ Hi • If number of characters to output is less then that amount of characters in the output the field will automatically expand to fit the output.

10. Fixed • What happens when we use floating-point values and setw? • Take the value 4.85, it takes four output positions to print this to the screen. • Another problem with float-point values is that large values are printed in Scientific notation. • 123456789.5 may print as 1.23457e+08 on some systems. • Can use fixed to force all subsequent floating-point output to appear in decimal form instead of scientific notation. • cout << fixed << 3.8 * x; • However, if the number is whole number it will not print as a floating-point number.

11. Showpoint • showpointforces decimal points to be displayed in subsequent floating-point output, even for whole numbers. • cout << showpoint << someFloat; • What if we want just two decimal places?

12. setprecision • setprecisionspecifies the desired number of decimal places. • REMAINS IN EFFECT for all subsequent output. • Should use setprecisionand the fixed together to get correct results.

13. Additional String Operations • .at() • Included instead to the cctypeheader file; • #include <cctype> • toupper() • tolower()

14. At function • At function allows for individual character access in a string. • str1.at(pos); • pos being the character position you want to access. • This returns the character at that location within the string. • string str1 = “Robert”; • char letter = str1.at(0); • The variable letter now is holding the character ‘R’;

15. toupper • toupper(ch) returns the uppercase equivalent of ch, if chis a lowercase character; ch, otherwise. • Ex. • toupper(‘r’) returns ‘R’ • toupper(‘R’) returns ‘R’

16. tolower • tolower(ch) returns the lowercase equivalent of ch, if chis an uppercase letter; ch, otherwise. • Ex. • tolower(‘R’) returns ‘r’ • tolower(‘r’) returns ‘r’