Numeric Types, Expressions, and Output

Numeric Types, Expressions, and Output Robert reaves

Additional String Operations • Four functions that we will use to operate on strings: • length • size • find • substr

Length Function • When applied to a string variable, it returns an unsigned integer value that equals the number of characters currently in the string. • If myName is a string variable, a call looks like this: • myName.length(); • Use parentheses to signify an empty argument list. • This is a value-returning function, so the call must appear within an expression.

Dot Notation • Why the call to this function so weird? • Certain programmer-defined data types, such as strings, have functions that are associated with them and the dot notation is required in the calls. • myName.length(); • Dot notation is the dot (period) between the variable name and the function name. • What is we don’t use the “dot” and say: • length();

Size Function • Same as length function. • This was to accommodate both terms, since people say size and length interchangeably. • Example: • myName.size(); • Returns unsigned-integer value, thus you must declare results to be of type int. • string firstName; • intlen; • firstName = “Robert”; • len = firstName.length(); //len = firstName.size();

Find Function • Find function searches a string to find the first occurrence of a particular substring and returns an unsigned integer value. • Takes one argument, a literal string or a string expression. • Ex: • str1.find(“the”); • str1.find(str2); • str1.find(str2 + “abc”); • str1 is searched to see if substring can be found within it. • If so, returns the position in str1 where the match beings. (Position start at 0) • Else returns “npos”, meaning not a position within the string” • Evaluates to something like 4294967295 • Has to match exact.

Find Function • Find function can also be a char value, in this case it returns the position of the first occurrence of that character within the string else “npos”. • Only returns the FIRST matched position.

Substr Function • Substrfunction returns a particular substring of a string. • Ex: • String myString = “Hello, my name is Robert.”; • myString.substr(5, 20); • First argument is an unsigned integer that specifies a position within the string, and the second is an unsigned integer that specifies the length of the desired substring. • Returns the piece of the string that starts at the specified location and continues for the number of characters given by the second argument. • DOESN’T CHANGE YOUR ORIGINAL STRING

Numeric Data Types • Data types: • char, short, int, long • Are known as integral types (or integer types) because they refer to integer values, in other words WHOLE NUMBERS. • ex: • 22 • 16 • 1 • 0 • Commas are NOT ALLOWED • Minus sign preceding an integer will make it negative.

Numeric Data Types • Exception to this is when you add the reserved word unsigned to the data type name. • Ex: unsigned int • Assumed to only be positive or zero. • Used for specialized situations. • Meaning you won’t use these in here. • Each data type is intended to represent different sizes of integers, however this is machine dependent.

Numeric Data Types • Wait, why is a char an integer type? • C++ classifies char as an integral type so it can be used to store integer values with a very limited range • -128 to 127

Numeric Data Types • Float, or floating type are used to represent real numbers. • Have an integer part and a fractional part, with a decimal between. • Ex: • 18.0 • 127.54 • .8 • Computer cannot always represent exactly. • Slight inaccuracies in the rightmost fractional digits are to be expected and are not the result of programmer error. • Ex: • 4.8 might be 4.79999998

Named Constant Declartions • Just to show you can make constant variables of all data types. • const float PI = 3.14159; • const float E = 2.71828; • constint MAX_SCORE = 100; • constint MIN_SCORE = -100; • const char LETTER = ‘W’; • const string NAME = “Elizabeth”;

Arithmetic Operators • Operators allowed in an expression depend on the data types of the constants and variables in the expressions. • Arithmetic operators: • + Unary Plus • - Unary minus • + Addition • - Subtraction • * Multiplication • / • Floating-point division (floating-point result) • Integer division (no fractional part) • % Modulus (remainder from integer division.

Arithmetic Operators • Unary Operators an operator that has just one operand. • Ex: • -54 • +259.65 • -rate (can use on variables) • Rarely use unary plus, numeric constant is assumed to be positive. • Binary Operators an operator that has two operands.

Arithmetic Operators • % (modulus) is only used with integers. • Gives only the remainder. • 10 / 7 = 3 • / (division) can be used with integers or float • Integer division yields ONLY the quotient • 10 / 7 = 1 • Floating point yields a floating point result • 10.0 / 7.0 = 1.3

Increment and Decrement Operators • C++ provides increment and decrement operators • ++ increment • -- decrement • Unary operators take a single variable as an operand. • For int and float operands, the effect is to add 1 or subtract 1 from the operand. • If numcurrently contains 8, what would this statement yield? • num++; • and • num--;

Increment and Decrement Operators • The ++ and – operators can be either prefix operators: • ++num; • or postfix operators: • num++;

Library Functions • C++ system includes a standard library-a large collection of prewritten functions, data types, and other times that any C++ programmer may use. • The functions in library are divided into separate files called header files. • Ex: • #include <cmath> • This library had this like sqrt() and abs()

Numeric Types, Expressions, and Output