Learn Ruby the Hard Way: Words & Symbols

Question 1

terminal:

irb

Answer 1

into ruby realm!

Question 2

mkdir NAME

Answer 2

Make Directory

Question 3

cd NAME

Answer 3

Change Directory

Question 4

puts

Answer 4

write out string and create new line

Question 5

ruby ex1.rb

Answer 5

run ex1.rb

Answer 6

Caret character, points out where the error is

Question 7

#

Answer 7

Anything after this on the same line is a comment

Question 8

+

Answer 8

plus which can add two things

Question 9

-

Answer 9

minus which can subtract two things

Question 10

/

Answer 10

slash which can divide two things

Question 11

*

Answer 11

asterisk which can multiply two things

Question 12

%

Answer 12

percent which does the modulo thing and string substitution; example

“We are a %s and %s.” % [animal1, animal2]

Question 13

<

Answer 13

less than

Question 14

>

Answer 14

greater than

Question 15

<=

Answer 15

less-than-equal

Question 16

> =

Answer 16

greater-than-equal

Question 17

=

Answer 17

equal, set a variable

Question 18

_

Answer 18

underscore

Question 19

format string

Answer 19

“ANYTHINGINHERE”

Question 20

string

Answer 20

something a human will read or be given

Question 21

string interpolation

Answer 21

put a defined string within a string using “#{}”

Question 22

\n

Answer 22

put a new line character into the string at that point.

Question 23

<<WHATEVER
text 
text
WHATEVER

Answer 23

document syntax, which uses «NAME and works like a string, but you also can put as many lines of text you as want until you type NAME again.

Question 24

\

Answer 24

These two characters will print just one back-slash.

Question 25

\

Answer 25

Escape technique.
To solve this problem you escape double-quotes and single-quotes so Ruby knows to include in the string. Here’s an example:

“I am 6’2" tall.” # escape double-quote inside string
‘I am 6'2” tall.’ # escape single-quote inside string

Question 26

\t

Answer 26

tabbed

Question 27

print

Answer 27

Notice that we are using print instead of puts to do the prompting. print doesn’t add a new line automatically, so your answer can go on the same line as the question. puts on the other hand, adds a newline automatically.

Question 28

.gets

Answer 28

takes user input and puts on new line

Question 29

.chomp

Answer 29

since .gets automatically adds a new line this method will destroy that new line, putting the response on the same line

Question 30

require “whatever”

Answer 30

his is how you add features to your script from the Ruby feature set or other sources (e.g., Ruby Gems, stuff you wrote yourself). Rather than give you all the features at once, Ruby asks you to say what you plan to use. This keeps your programs small, but it also acts as documentation for other programmers who read your code later.

feature = libraries = modules

Question 31

feature

Answer 31

= libraries = modules

Question 32

argument

Answer 32

You know how you type ruby ex13.rb to run the ex13.rb file? Well the ex13.rb part of the command is called an “argument”
What we’ll do now is write a script that also accepts arguments.

Type this program and I’ll explain it in detail:

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first, second, third = ARGV 

puts “The script is called: #{$0}”
puts “Your first variable is: #{first}”
puts “Your second variable is: #{second}”
puts “Your third variable is: #{third}”
The ARGV is the “argument variable”, a very standard name in programming, that you will find used in many other languages.

Question 33

ARGV

Answer 33

The ARGV is the “argument variable”, a very standard name in programming, that you will find used in many other languages. It’s in all caps because it’s a constant, meaning you shouldn’t change the value once it’s been assigned. This variable holds the arguments you pass to your Ruby script when you run it.

Question 34

STDIN

Answer 34

Also notice that we’re using STDIN.gets instead of plain ‘ol gets. That is because if there is stuff in ARGV, the default gets method tries to treat the first one as a file and read from that. To read from the user’s input (i.e., stdin) in such a situation, you have to use it STDIN.gets explicitly.

Question 35

prompt

Answer 35

puts forward something before the user input, like >

Question 36

Hard coding

Answer 36

“Hard coding” means putting some bit of information that should come from the user as a string right in our program. That’s bad because we want it to load other files later. The solution is to use ARGV and STDIN.gets to ask the user what file they want instead of “hard coding” the file’s name.

Question 37

txt = File.open(filename)

puts txt.read()

Answer 37

We call a function on txt. What you got back from open is a file, and it’s also got commands you can give it. You give a file a command by using the . (dot or period), the name of the command, and parameters. Just like with File.open. The difference is that when you say txt.read() you are saying, “Hey txt! Do your read command with no parameters!”
Reads the contents of the file, you can assign the result to a variable.

Question 38

.close()

Answer 38

close files you open

Closes the file. Like File->Save.. in your editor.

Question 39

.readline()

Answer 39

Reads just one line of a text file.

Question 40

.truncate

Answer 40

Empties the file, watch out if you care about the file.

Question 41

.write(stuff)

Answer 41

write stuff to file

Question 42

File.open(filename, ‘w’)

Answer 42

instead of opening regularly which is in read for, open in write form

Question 43

File.exists?

Answer 43

True if it exists, False if it doesn’t

Question 44

type WHAT.txt

Answer 44

output the text

Question 45

Functions

Answer 45

They name pieces of code the way variables name strings and numbers.

They take arguments the way your scripts take ARGV.

Using #1 and #2 they let you make your own “mini scripts” or “tiny commands”.

Question 46

Run, Call, Use a function?

Answer 46

“To ‘run’, ‘call’, or ‘use’ a function all mean the same thing.”

Question 47

IO::SEEK_SET

Answer 47

IO::SEEK_SET | Seeks to the absolute location given by amount

Question 48

What’s the difference between %s and %d?

Answer 48

%s expects a string, while %d expects a number

Question 49

alias

Answer 49

associate a method and make it synonymous with another method.

To alias a method or variable name in Ruby is to create a second name for the method or variable. Aliasing can be used either to provide more expressive options to the programmer using the class, or to help override methods and change the behavior of the class or object.

Question 50

and

Answer 50

flow control operator with low precedence that means do x and do y. Not to be confused with &&, which is a boolean operator with high precedence.

Question 51

BEGIN

Answer 51

Designates, via code block, code to be executed unconditionally before sequential execution of the program begins. Sometimes used to simulate forward references to methods (comes from http://ruby-doc.org/docs/keywords/1.9/Object.html#method-i-BEGIN,and I’m only slightly sure of what it means).

Question 52

begin

Answer 52

Together with end, delimits what is commonly called a “begin” block (to distinguish it from the Proc type of code block).

Question 53

break

Answer 53

terminates execution of a code block and jumps out of it. Think of a case statement, as that’s where I’m most familiar with seeing it being used.

Question 54

case

Answer 54

INVESTIGATE

Question 55

class

Answer 55

defines an object and its methods that can be used by ruby

Question 56

def

Answer 56

used to define a function

Question 57

defined?

Answer 57

determines if a method refers to something directly (a string, a number, etc.)

Question 58

do

Answer 58

execute everything that follows as if it were part of the same block

Question 59

END

Answer 59

defines a section of code that can be run at the end of a code block

Question 60

end

Answer 60

end of a block of code

Question 61

ensure

Answer 61

usually run with a rescue statement, even if the rescue statement doesn’t get run, the ensure statement will run

Question 62

for

Answer 62

keyword to define the start of a loop

Question 63

in

Answer 63

run the steps in the for loop that match this condition

Question 64

module

Answer 64

synonymous with function, it’s a scope where local variables are not aware of other variables

Question 65

not

Answer 65

is not this value

Question 66

redo

Answer 66

re-executes a code block without regard to conditions of variables or state of the program

Question 67

rescue

Answer 67

error handling section of code

Question 68

retry

Answer 68

associated with rescue, has the program try the section of code where the rescue statement resides agan

Question 69

return

Answer 69

value sent out from a function to the main routine

Question 70

self

Answer 70

the area of code being rn at any given time

Question 71

super

Answer 71

INVESTIGATE

Question 72

then

Answer 72

makes possible a conditional statement on a single line (i.e. without having to use a semi-colon)

Question 73

undef

Answer 73

dereference a method or class for use in a given scope

Question 74

yield

Answer 74

called from inside a method body, yields control to the code block (If any) supplied as part of the method call. if no code block has been supplied, calling yield raises an exception.

Question 75

constants

Answer 75

data type that starts with a capital letter. if value is changed ruby will warn you that you have changed a constant.
Pi = 3.14

Question 76

string

Answer 76

a collection of character

a = “hello there”

Question 77

numbers

Answer 77

any digital value

a= 1, b = 24

Question 78

ranges

Answer 78

a grouping of numbers (1..10) or (1…10)

Question 79

arrays

Answer 79

a special container that can contain many values under the same variable name value

array = [“one”, 2, “three”, 4]

Question 80

hashes

Answer 80

similar to an array, but with a way to associate values

hash = {“dog” => “canine”, “cat” => “feline”}

Question 81

\a

Answer 81

INVESTIGATE

Question 82

\f

Answer 82

INVESTIGATE

Question 83

\n

Answer 83

prints a new line

Question 84

\r

Answer 84

prints a literal carriage return

Question 85

\t

Answer 85

tab

Question 86

\v

Answer 86

vertical tab

Question 87

::

Answer 87

call a constant value

Question 88

[]

Answer 88

element set, used with arrays

Question 89

**

Answer 89

exponent arithmetic operator

Question 90

-(unary)

Answer 90

INVESTIGATE

Question 91

+(unary)

Answer 91

INVESTIGATE

Question 92

!

Answer 92

logical not operator

Question 93

~

Answer 93

binary ones complement operator

Question 94

«

Answer 94

binary left shift operator

Question 95

> >

Answer 95

binary right shift operator

Answer 96

combined comparison operator
a bigger than b, 1
equal, 0
b bigger than a, -1

Question 97

===

Answer 97

special equals option when used within a case statement

Question 98

!=

Answer 98

not equal

Question 99

%w

Answer 99

white space separated array
square brackets %w[…], curly braces %w{…} or even something like exclamation marks %w!…!. All of these have the same behavior (returning an array)