Review Ruby

Question 1

puts “put s”

Answer 1

• ‘prints’ the following on the screen

Question 2

#

Answer 2

• hash, pound, octothorpe

- starts a comment line or used to disable a line of code

Question 3

“…”

‘…’

Answer 3

• a string of text
• single quotes do things different. Can be used around a variable in a string, printing the output with single quotes showing

Question 4

\+
-
/
*
%
<
><=
>=

PEDMAS
PE(M&D) (A&S)

Answer 4

-plus
- minus
- slash (divide)
- asterisk (multiply)
- percent
(modulus - x divided by y with j remaining) The result of % is the j part , the remainder

Question 5

{…}

Answer 5

• this is the format for inserting Ruby computations inside text strings. The result of the computation in the ‘printed’ string

Question 6

Xxx_yyy

Answer 6

Underscore - puts an imaginary space between words in variable names

ex: carpool_capacity

Question 7

4 vs 4.0

Answer 7

Integer vs floating point number

Question 8

= (…)

Answer 8

= equals is used to give data (numbers, strings, etc. ) names

-sets a variable

Question 9

==

Answer 9

• double equal tests whether two things have the same value

Question 10

x=100 vs x = 100?

Answer 10

• it is bad form to leave out the spaces

Question 11

variable

Answer 11

• any line of code where you set a name = (equal) to a value

ex. type_of_fish = 10

Question 12

print vs puts

Answer 12

puts has a linefeed in it

Print does not

Question 13

{} or %{} ?

Answer 13

Always use #{} to format strings

%{} is used when you want to apply strings multiple times

Question 14

\n

%q{
-
-
-
}

Answer 14

• escape sequence … linefeed

Print a multi line string

Question 15

“””

Answer 15

• triple quotes works like a string, but you put as many lines of text as you want until you type

“”” again

note: use ‘’’ when you need a multiline string that contains #{} formatting, but you don’t want them to be processed yet or at all. Use “”” For all other multiline strings.

Question 16

gets.chomp

Answer 16

gets retrieves a line of text input from the user AND includes a trailing linefeed

chomp suppresses the linefeed

Question 17

gets.chomp.to_i

Answer 17

Get a string from the user

chomp off the \n and convert too an integer

Question 18

ARGV

ARGV.first. vs ARGV first 2nd 3rd etc.

Answer 18

Argument variable

• must pass x command line arguments
  ex. Ruby ex13.rb 1st 2nd 3rd etc.

Note: ARGV gets input from the command line while gets.chomp input comes in via the keyboard while the script is running.

ARGV.first is for only one argument

Question 19

$stdin

Answer 19

Standard input is stream data

Question 20

close

read

readline

truncate

write(‘stuff’)

seek(0)

Answer 20

• closes the file
• reads the contents of the file. You can send the results to a variable.
• reads just one line of a text file.
• empties the file. Watch out if you care about the file.
• writes “stuff“ to the file.

Move the read/write location to the beginning of the file.

Question 21

Modifiers

w

r

a

w+

Answer 21

• write
• read
• append
• will open file in read and write mode

Question 22

echo

cat

That;depends;on;how…

Answer 22

• ?
• concatenate, an old command that puts files together. Mostly it’s just an easy way to print a file to the screen.

You make several lines of into fewer by using ;

Question 23

functions

def

Answer 23

• I name pieces of cove the way variables name strings in numbers.
• They take arguments the way scripts take ARGV.
• Using one and two, they let you make your own mini scripts or tiny commands