For this exercise I have to go trough a list of symbols and words and try to recall what they are/do from memory. Then I have to look them up and test them out to make sure they do what I think they do.
KEYWORDS
Explanations of all the keywords can be found on ruby-doc.org
| KEYWORD | DESCRIPTION | EXAMPLE |
|---|---|---|
| BEGIN | Run this block when the script starts. Before sequential execution of the program starts. | BEGIN { puts "hi" } |
| END | Run this block when the script is done. Prior to the termination of the program. | END { puts "hi" } |
| alias | Create another name for a function. | alias X Y |
| and | Logical and, but lower priority than &&. | puts "Hello" and "Goodbye" |
| begin | Start a block, usually for exceptions. | begin end |
| break | Break out of a loop right now. Prevents a continuous loop. | while true; break; end |
| case | Case style conditional, like an if. | case X; when Y; else; end |
| class | Define a new class. | class X; end |
| def | Define a new function. | def X(); end |
| defined? | Is this class/function/etc. defined already? Used to test if the expression is being used. If not it returns nil | defined? Class == "constant" |
| do | Create a block that maybe takes a parameter. | (0..5).each do |x| puts x end |
| else | Else conditional. | if X; else; end |
| elsif | Else if conditional | if X; elsif Y; else; end |
| end | Ends blocks, functions, classes, everything. | begin end # many others |
| ensure | Run this code whether an exception happens or not. Code in an ensure clause is guaranteed to be executed. | begin ensure end |
| for | For loop syntax. The .each syntax is preferred. | for X in Y; end |
| if | If conditional. | if X; end |
| in | In part of for-loops. | for X in Y; end |
| module | Define a new module. Takes a constant as its argument. | module X; end |
| next | Skip to the next element of a .each iterator. | (0..5).each {|y| next } |
| not | Logical not. But use ! instead. | not true == false |
| or | Logical or. || has precedence. | puts "Hello" or "Goodbye" |
| redo | Rerun a code block exactly the same. | (0..5).each {|i| redo if i > 2} |
| rescue | Run this code if an exception happens. | begin rescue X; end |
| retry | In a rescue clause, says to try the block again. | (0..5).each {|i| retry if i > 2} |
| return | Returns a value from a function. Mostly optional. | return X |
| self | The current object, class, or module. | defined? self == "self" |
| super | The parent class of this class. | super |
| then | Can be used with if optionally. Allows you to make one-line conditionals without semi-colons. | if true then puts "hi" end if a > b then puts "a wins!" end |
| undef | Remove a function definition from a class. | undef X |
| unless | Inverse of if. | unless false then puts "not" end |
| until | Inverse of while, execute block as long as false. | until false; end |
| when | Part of case conditionals. | case X; when Y; else; end |
| while | While loop. | while true; end |
| yield | Pause and transfer control to the code block. | yield |
DATA TYPES
| TYPE | DESCRIPTION | EXAMPLE |
|---|---|---|
| true | True boolean value. | true or false == true |
| false | False boolean value. | false and true == false |
| nil | Represents “nothing” or “no value”. | x = nil |
| strings | Stores textual information. | x = "hello" |
| numbers | Stores integers. *note I couldn’t find ‘numbers’ specifically. Everything linked back to Integers. | i = 100 |
| floats | Stores decimals. | i = 10.389 |
| arrays | Stores a list of things. | j = [1,2,3,4] |
| hashes | Stores a key = value mapping of things. | e = {'x' => 1, 'y' => 2} |
ESCAPES
| ESCAPE | DESCRIPTION |
|---|---|
| \\ | Backslash |
| \' | Single-quote |
| \" | Double-quote |
| \a | Bell |
| \b | Backspace |
| \f | Formfeed |
| \n | Newline |
| \r | Carriage |
| \t | Tab |
| \v | Vertical tab |
OPERATORS
| OPERATOR | DESCRIPTION | EXAMPLE |
|---|---|---|
| + | Add | 2 + 4 == 6 |
| - | Subtract | 2 - 4 == 2 |
| * | Multiply | 2 * 4 == 8 |
| ** | Power of | 2 ** 4 == 16 |
| / | Divide | 2 / 4.0 == 0.5 |
| % | Modulus | 2 % 4 == 2 |
| > | Greater than | 4 > 4 == false |
| . | Dot access | "1".to_i == 1 |
| :: | Colon access | Module::Class |
| [] | List brackets | [1,2,3,4] |
| ! | Not | !true == false |
| < | Less than | 4 < 4 == false |
| > | Greater than | 4 < 4 == false |
| >= | Greater than equal | 4 >= 4 == true |
| <= | Less than equal | 4 <= 4 == true |
| <=> | Comparison | 4 <=> 4 == 0 |
| == | Equal | 4 == 4 == true |
| === | Equality | 4 === 4 == true |
| != | Not equal | 4 != 4 == false |
| && | Logical and (higher precedence) | true && false == false |
| || | Logical or (higher precedence) | true || false == true |
| .. | Range inclusive | (0..3).to_a == [0, 1, 2, 3] |
| ... | Range non-inclusive | (0...3).to_a == [0, 1, 2] |
| @ | Object scope | @var ; @@classvar |
| @@ | Class scope | @var ; @@classvar |
| $ | Global scope | $stdin |
Anxious Designer Girl 