Enumerable

Question 1

Ruby Enumerable

returns true if the block never returns false or nil

Answer 1

all? { |obj| block } => true or false

Question 2

Ruby Enumerable

returns true if the block ever returns a value other than false or nil

Answer 2

any? { |obj| block } => true or false

Question 3

Ruby Enumerable

returns a new array with the results of running block once for every element in enum

Answer 3

map { |obj| block } => array

Question 4

Ruby Enumerable

returns the number of elements for which the block yields a true value

Answer 4

count { |obj| block } => int

Question 5

Ruby Enumerable

returns the first for which block is not false

Answer 5

find(ifnone = nil) { |obj| block } => obj or nil

Question 6

Ruby Enumerable

alias for select

Answer 6

find_all { |obj| block } => array

Question 7

Ruby Enumerable

groups the collection by result of the block; returns a hash where the keys are the evaluated result from the block and the values are arrays of elements in the collection that correspond to the key

Answer 7

group_by { |obj| block } => a_hash

ex

(1..6).group_by { |i| i%3 } #=> {0=>[3, 6], 1=>[1, 4], 2=>[2, 5]}

Question 8

Ruby Enumerable

returns true if any member of enum equals obj

Answer 8

include?(obj) => true or false

Question 9

Ruby Enumerable

combines all elements of enum by applying a binary operation, specified by a block or a symbol that names a method or operator

Answer 9

inject(initial, sym) => obj inject(initial) { |memo, obj| block } => obj

ex

(5..10).inject(0, &:+) => 45 (5..10).inject(0) { |memo, num| memo + num } => 45

Question 10

Ruby Enumerable

returns the object in enum with the maximum value; can use a block to implement a \<=\> b

Answer 10

max(n) { |a,b| block } => obj

ex

a = %w(albatross dog horse)

a. max #=> “horse”
a. max { |a, b| a.length b.length } #=> “albatross”

Question 11

Ruby Enumerable

alias of include?

Answer 11

member?(obj) => true or false

Question 12

Ruby Enumerable

opposite of max

Answer 12

min(n) { |a,b| block }

Question 13

Ruby Enumerable

returns true if the block never returns true for all elements

Answer 13

none? { |obj| block } => true or false

Question 14

Ruby Enumerable

returns true if the block returns true exactly once

Answer 14

one? { |obj| block } => true or false

Question 15

Ruby Enumerable

opposite of select

Answer 15

reject { |obj| block } => array

Question 16

Ruby Enumerable

returns an array containing all elements of enum for which the given block returns a true value

Answer 16

select { |obj| block } => array

Question 17

Ruby Enumerable

returns an array containing the items in enum sorted, either according to their own method, or by using the results of the supplied block

Answer 17

sort { |a, b| block } => array

Question 18

Ruby Enumerable

takes one element from enum and merges corresponding elements from each args. This generates a sequence of n-element arrays, where n is one more than the count of arguments

Answer 18

zip(arg, …) => an_array_of_array

zip(arg, …) { |arr| block } => nil

ex

a = [4, 5, 6]

b = [7, 8, 9]

a.zip(b) #=> [[4, 7], [5, 8], [6, 9]]

[1, 2, 3].zip(a, b) #=> [[1, 4, 7], [2, 5, 8], [3, 6, 9]]

[1, 2].zip(a, b) #=> [[1, 4, 7], [2, 5, 8]]

a.zip([1, 2], [8]) #=> [[4, 1, 8], [5, 2, nil], [6, nil, nil]]

c = []

a.zip(b) { |x, y| c nil

c #=> [11, 13, 15]

Question 19

Ruby Enumerable

iterates the given block for each element with an arbitrary object given, and returns the initially given object

Answer 19

each_with_object(obj) { |element, object| block } => obj

ex

evens = (1..10).each_with_object([]) { |i, a| a [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]

Question 20

Ruby Enumerable

all? { |obj| block } => true or false

Answer 20

returns true if the block never returns false or nil

Question 21

Ruby Enumerable

any? { |obj| block } => true or false

Answer 21

returns true if the block ever returns a value other than false or nil

Question 22

Ruby Enumerable

map { |obj| block } => array

Answer 22

returns a new array with the results of running block once for every element in enum

Question 23

Ruby Enumerable

count { |obj| block } => int

Answer 23

returns the number of elements for which the block yields a true value

Question 24

Ruby Enumerable

find(ifnone = nil) { |obj| block } => obj or nil

Answer 24

returns the first for which block is not false

Question 25

Ruby Enumerable

find_all { |obj| block } => array

Answer 25

alias for select

Question 26

Ruby Enumerable

group_by { |obj| block } => a_hash

ex

(1..6).group_by { |i| i%3 } #=> {0=>[3, 6], 1=>[1, 4], 2=>[2, 5]}

Answer 26

groups the collection by result of the block; returns a hash where the keys are the evaluated result from the block and the values are arrays of elements in the collection that correspond to the key

Question 27

Ruby Enumerable

include?(obj) => true or false

Answer 27

returns true if any member of enum equals obj

Question 28

Ruby Enumerable

inject(initial, sym) => obj inject(initial) { |memo, obj| block } => obj

ex

(5..10).inject(0, &:+) => 45 (5..10).inject(0) { |memo, num| memo + num } => 45

Answer 28

combines all elements of enum by applying a binary operation, specified by a block or a symbol that names a method or operator

Question 29

Ruby Enumerable

max(n) { |a,b| block } => obj

ex

a = %w(albatross dog horse)

a. max #=> “horse”
a. max { |a, b| a.length b.length } #=> “albatross”

Answer 29

returns the object in enum with the maximum value; can use a block to implement a \<=\> b

Question 30

Ruby Enumerable

member?(obj) => true or false

Answer 30

alias of include?

Question 31

Ruby Enumerable

min(n) { |a,b| block }

Answer 31

opposite of max

Question 32

Ruby Enumerable

none? { |obj| block } => true or false

Answer 32

returns true if the block never returns true for all elements

Question 33

Ruby Enumerable

one? { |obj| block } => true or false

Answer 33

returns true if the block returns true exactly once

Question 34

Ruby Enumerable

reject { |obj| block } => array

Answer 34

opposite of select

Question 35

Ruby Enumerable

select { |obj| block } => array

Answer 35

returns an array containing all elements of enum for which the given block returns a true value

Question 36

Ruby Enumerable

sort { |a, b| block } => array

Answer 36

returns an array containing the items in enum sorted, either according to their own method, or by using the results of the supplied block

Question 37

Ruby Enumerable

zip(arg, …) => an_array_of_array

zip(arg, …) { |arr| block } => nil

ex

a = [4, 5, 6]

b = [7, 8, 9]

a.zip(b) #=> [[4, 7], [5, 8], [6, 9]]

[1, 2, 3].zip(a, b) #=> [[1, 4, 7], [2, 5, 8], [3, 6, 9]]

[1, 2].zip(a, b) #=> [[1, 4, 7], [2, 5, 8]]

a.zip([1, 2], [8]) #=> [[4, 1, 8], [5, 2, nil], [6, nil, nil]]

c = []

a.zip(b) { |x, y| c nil

c #=> [11, 13, 15]

Answer 37

takes one element from enum and merges corresponding elements from each args. This generates a sequence of n-element arrays, where n is one more than the count of arguments

Question 38

Ruby Enumerable

each_with_object(obj) { |element, object| block } => obj

ex

evens = (1..10).each_with_object([]) { |i, a| a [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]

Answer 38

iterates the given block for each element with an arbitrary object given, and returns the initially given object