recitation3 notes

2502125 useafloatasatleastoneoperandtostoptruncation

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Unformatted text preview: bles a. An instance variable is a variable that is referenced via an instance of a class and therefore belongs to a given object. b. It is always prefixed by a single at (@) sign c. Example: @hello = 6170 d. You can access instance variables from outside of their class only by accessor methods 4. Class Variables a. A instances of a class. Only one copy of a class variable exists for a given class. b. It is always prefixed by two at signs (@@) c. You have to initialize a class variable before you use it d. Example: @@times = 0 5. Global Variables a. Global variables are available globally to a program, inside any structure. Their scope is the whole program. b. It is always prefixed by a dollar sign ($) c. Example: $amount = “0.00” Topic 6: Math 1. Converting Numbers a. Integer(1.4) => 1 b. Integer(“256”) => 256 c. Integer(“0b100”) => 8 d. Integer(?z) => 122 // converts a floating-point number // converts a string // converts a binary number from string // converts a character to ASCII 2. Basic Math Operators: a. Use + , - , * , / for addition, subtraction, multiplication, and division 5 b. Use ** for exponent c. Use % for modulo 3. Division and Truncation a. 25 / 2 => 12 // Integer division always rounded down b. 25.0 / 2 => 12.5 // Use a float as at least one operand to stop truncation 4. Ranges a. The range operator . . means an inclusive range of numbers. Example: 1 . . 10 = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) b. The range operator . . . means a range of numbers excluding the last one Example: 1 . . . 10 = (1, 2, 3, 4, 5, 6, 7, 8, 9) c. Creating an array of a range of numbers: (1 . . 9).to_a => [1, 2, 3, 4, 5, 6, 7, 8, 9] //.to_a means “to array” 5. Useful Math methods a. Absolute value: -40.abs => 40 b. Ceiling: 4.65.ceil => 5 c. Floor: 4.65.floor => 4 d. Rounding: 100.45.round => 100 Topic 7: String 1. Basic string functions: a. title = String.new b. title.empty? c. title.length // sets title = “” // returns boolean showing whether title is empty (“”) // returns length of title 2. Concatenating Strings a. “Hello,” “ “ “Matz” “!” b. “Hello,” + “ “ + “Matz” + “!” c. “Hello, “ << “Matz!” d. “Hello, “.concat “Matz!” // Creates “Hel...
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