Array

Question 1

Ruby Array

return the first n elements of an array

Answer 1

take(n) => new_ary

Question 2

Ruby Array

return a new array containing elements common to the two arrays

Answer 2

ary & other_ary => new_ary

Question 3

Ruby Array

return a new array built by concatenating the two arrays together to produce a third array

Answer 3

concat(other_ary) => ary

Question 4

Ruby Array

return a new array that is a copy of the original array, removing any items that also appear in other_ayr

Answer 4

ary - other_ary => new_ary

Question 5

Ruby Array

append - pushes the given object to the end of this array

Answer 5

ary << obj => ary

Question 6

Ruby Array

search through an array whose elements are also arrays comparing obj with the first element of each contained array; return the first contained array that matches, or nil if no match is found

Answer 6

assoc(obj) => element_ary or nil

Question 7

Ruby Array

return the element at index; a negative index counts from the end of self; return nil if the index is out of range

Answer 7

at(index) => obj or nil

Question 8

Ruby Array

remove all elements of self

Answer 8

clear => ary

Question 9

Ruby Array

yield all combinations of length n of elements from the array

Answer 9

combination(n) => Enumerator

Question 10

Ruby Array

return a copy of self with all nil elements removed

Answer 10

compact => new_ary

Question 11

Ruby Array

alias for Array#concat

Answer 11

ary + other_ary => new_ary

Question 12

Ruby Array

return the number of elements; if an argument is given, return the number of elements that == obj; if a block is given, return the number of elements for which the block returns true

Answer 12

count => int

count(obj) => int

count { |item| block } => int

Question 13

Ruby Array

call the given block n times for each element or forever if nil is given

Answer 13

cycle(n=nil) { |obj| block }

Question 14

Ruby Array

delete all items from self that == obj

Answer 14

delete(obj) => item or nil

Question 15

Ruby Array

delete the element at the specified index, returning that element or nil if the index is out of range

Answer 15

delete_at(index) => obj or nil

Question 16

Ruby Array

return a new array containing elements in self for which the given block is not true

Answer 16

reject { |item| block } => new_ary

Question 17

Ruby Array

drop first n elements from ary and returns the remaining elements in an array

Answer 17

drop(n) => new_ary

Question 18

Ruby Array

drop elements up to, but not including, the first element for which the block returns nil or false and return an array containing the remaining elements

Answer 18

drop_while { |obj| block } => new_ary

Question 19

Ruby Array

call the given block once for each element in self, passing that element as a parameter; return the array itself

Answer 19

each { |item| block } => ary

Question 20

Ruby Array

same as Array#each, but passes the index of the element instead of the element itself

Answer 20

each_index { |index| block } => ary

Question 21

Ruby Array

return true if self contains no elements

Answer 21

empty? => true or false

Question 22

Ruby Array

set the selected elements of self to obj; if a block is given, fills the array with the value of the block, which is passed the index of each element to be filled

Answer 22

fill(obj) => ary

fill(obj, start [, length]) => ary

fill(obj, range) => ary

fill { |index| block } => ary

fill(start [, length]) { |index| block} => ary

fill(range) { |index| block } => ary

Question 23

Ruby Array

return the index of the first element that == obj; if a block is given, return the index of the first element for which the block returns true

Answer 23

find_index(obj) => int or nil

find_index { |item| block } => int or nil

Question 24

Ruby Array

return the first n elements of self

Answer 24

first => obj or nil

first(n) => new_ary

Question 25

Ruby Array

return a new array that is a one-dimensional flattening of self; optional level argument determines the level of recursion to flatten

Answer 25

flatten => new_ary

flatten(level) => new_ary

Question 26

Ruby Array

return true if obj is present in self (any element == obj)

Answer 26

include?(obj) => true or false

Question 27

Ruby Array

return the index of the first element of self that == obj; if a block is given, return the first element for which the block returns true

Answer 27

index(obj) => int or nil

index { |item| block } => int or nil

Question 28

Ruby Array

insert the given values before the element at the specified index; if a negative index is given, the elements are inserted after the element that index (i.e. -1 adds to the end of the array)

Answer 28

insert(index, obj…) => ary

Question 29

Ruby Array

return a string created by converting each element of self to a string, separated by the given separator or an empty string

Answer 29

join(separator=$,) => str

Question 30

Ruby Array

return the last n elements of self

Answer 30

last => obj or nil

last(n) => new_ary

Question 31

Ruby Array

return the number of elements in self

Answer 31

length => int

Question 32

Ruby Array

return a new array containing the values returned by the block, which is invoked once for each element of self

Answer 32

map { |item| block } => new_ary

Question 33

Ruby Array

yield all permutations of length n of the elements of self, then return the array itself

Answer 33

permutation(n) => Enumerator

permutation(n) { |p| block } => ary

Question 34

Ruby Array

remove the last n elements of self and return them

Answer 34

pop => obj or nil

pop(n) => new_ary

Question 35

Ruby Array

return an array of all combinations of elements of all arrays

Answer 35

product(other_ary, …) => new_ary

Question 36

Ruby Array

append - push the given object(s) on to the end of self, returning the array itself

Answer 36

push(obj, …) => ary

Question 37

Ruby Array

search through self whose elements are also arrays; compare obj with the second element of each contained array; return the first contained array that matches obj

Answer 37

rassoc(obj) => element or nil

Question 38

Ruby Array

yield all repeated combinations of length n of elements of self then returns the array itself

Answer 38

repeated_combination(n) => Enumerator

Question 39

Ruby Array

yield all repeated permuations of length n of the elements of self, then return the array itself

Answer 39

repeated_permutation(n) => Enumerator

Question 40

Ruby Array

return a new array containing self’s elements in reverse order

Answer 40

reverse => new_ary

Question 41

Ruby Array

same as Array#each but traverses self in reverse order

Answer 41

reverse_each { |item| block } => ary

Question 42

Ruby Array

return the index of the last element in self that == obj; if a block is given, return the index of the last element in self for which the block returns true

Answer 42

rindex(obj) => int or nil

rindex(obj) { |item| block } => int or nil

Question 43

Ruby Array

return a new array by rotating self so that the element at count is the first element of the new array

Answer 43

rotate(count=1) => new_ary

Question 44

Ruby Array

choose a random element or n random elements from self

Answer 44

sample => obj

sample(n) => new_ary

Question 45

Ruby Array

return a new array containing all elements of self for which the block returns a true value

Answer 45

select { |item| block } => new_ary

Question 46

Ruby Array

remove the first element of self and returns it (shifting all other elements down by one); returns nil if empty

Answer 46

shift => obj

Question 47

Ruby Array

return a new array with the elements of self shuffled

Answer 47

shuffle => new_ary

Question 48

Ruby Array

return a new array created by sorting self; comparisons done using ; if a block is given, it must implement a comparison between a and b and return a negative integer if a

Answer 48

sort => new_ary

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

Question 49

Ruby Array

return the first n elements of self

Answer 49

take(n) => new_ary

Question 50

Ruby Array

pass elements of self to the block until the block returns nil or false; returns an array of all prior elements

Answer 50

take_while { |obj| block } => new_ary

Question 51

Ruby Array

assume that self is an array of arrays and transposes rows and columns

Answer 51

transpose => new_ary

Question 52

Ruby Array

return a new array by removing duplicate values in self; if a block is given, use the return value of the block for comparison

Answer 52

uniq => new_ary

uniq { |item| block } => new_ary

Question 53

Ruby Array

prepend obj to the front of self, moving other elements upwards

Answer 53

unshift(obj, …) => ary

Question 54

Ruby Array

convert any arguments to arrays, then merges elements of self with corresponding elements from each argument; if a block is given, it’s invoked for each output array, otherwise an array of arrays is returned

Answer 54

zip(arg, …) => new_ary

zip(arg, …) { |arr| block } => nil

Question 55

Ruby Array

set union - return a new array by joining ary and other_ary, excluding any duplicates and preserving the order from the original array

Answer 55

ary | other_ary => new_ary

Question 56

Ruby Array

take(n) => new_ary

Answer 56

return the first n elements of an array

Question 57

Ruby Array

ary & other_ary => new_ary

Answer 57

return a new array containing elements common to the two arrays

Question 58

Ruby Array

concat(other_ary) => ary

Answer 58

return a new array built by concatenating the two arrays together to produce a third array

Question 59

Ruby Array

ary - other_ary => new_ary

Answer 59

return a new array that is a copy of the original array, removing any items that also appear in other_ayr

Question 60

Ruby Array

ary << obj => ary

Answer 60

append - pushes the given object to the end of this array

Question 61

Ruby Array

assoc(obj) => element_ary or nil

Answer 61

search through an array whose elements are also arrays comparing obj with the first element of each contained array; return the first contained array that matches, or nil if no match is found

Question 62

Ruby Array

at(index) => obj or nil

Answer 62

return the element at index; a negative index counts from the end of self; return nil if the index is out of range

Question 63

Ruby Array

clear => ary

Answer 63

remove all elements of self

Question 64

Ruby Array

combination(n) => Enumerator

Answer 64

yield all combinations of length n of elements from the array

Question 65

Ruby Array

compact => new_ary

Answer 65

return a copy of self with all nil elements removed

Question 66

Ruby Array

ary + other_ary => new_ary

Answer 66

alias for Array#concat

Question 67

Ruby Array

count => int

count(obj) => int

count { |item| block } => int

Answer 67

return the number of elements; if an argument is given, return the number of elements that == obj; if a block is given, return the number of elements for which the block returns true

Question 68

Ruby Array

cycle(n=nil) { |obj| block }

Answer 68

call the given block n times for each element or forever if nil is given

Question 69

Ruby Array

delete(obj) => item or nil

Answer 69

delete all items from self that == obj

Question 70

Ruby Array

delete_at(index) => obj or nil

Answer 70

delete the element at the specified index, returning that element or nil if the index is out of range

Question 71

Ruby Array

reject { |item| block } => new_ary

Answer 71

return a new array containing elements in self for which the given block is not true

Question 72

Ruby Array

drop(n) => new_ary

Answer 72

drop first n elements from ary and returns the remaining elements in an array

Question 73

Ruby Array

drop_while { |obj| block } => new_ary

Answer 73

drop elements up to, but not including, the first element for which the block returns nil or false and return an array containing the remaining elements

Question 74

Ruby Array

each { |item| block } => ary

Answer 74

call the given block once for each element in self, passing that element as a parameter; return the array itself

Question 75

Ruby Array

each_index { |index| block } => ary

Answer 75

same as Array#each, but passes the index of the element instead of the element itself

Question 76

Ruby Array

empty? => true or false

Answer 76

return true if self contains no elements

Question 77

Ruby Array

fill(obj) => ary

fill(obj, start [, length]) => ary

fill(obj, range) => ary

fill { |index| block } => ary

fill(start [, length]) { |index| block} => ary

fill(range) { |index| block } => ary

Answer 77

set the selected elements of self to obj; if a block is given, fills the array with the value of the block, which is passed the index of each element to be filled

Question 78

Ruby Array

find_index(obj) => int or nil

find_index { |item| block } => int or nil

Answer 78

return the index of the first element that == obj; if a block is given, return the index of the first element for which the block returns true

Question 79

Ruby Array

first => obj or nil

first(n) => new_ary

Answer 79

return the first n elements of self

Question 80

Ruby Array

flatten => new_ary

flatten(level) => new_ary

Answer 80

return a new array that is a one-dimensional flattening of self; optional level argument determines the level of recursion to flatten

Question 81

Ruby Array

include?(obj) => true or false

Answer 81

return true if obj is present in self (any element == obj)

Question 82

Ruby Array

index(obj) => int or nil

index { |item| block } => int or nil

Answer 82

return the index of the first element of self that == obj; if a block is given, return the first element for which the block returns true

Question 83

Ruby Array

insert(index, obj…) => ary

Answer 83

insert the given values before the element at the specified index; if a negative index is given, the elements are inserted after the element that index (i.e. -1 adds to the end of the array)

Question 84

Ruby Array

join(separator=$,) => str

Answer 84

return a string created by converting each element of self to a string, separated by the given separator or an empty string

Question 85

Ruby Array

last => obj or nil

last(n) => new_ary

Answer 85

return the last n elements of self

Question 86

Ruby Array

length => int

Answer 86

return the number of elements in self

Question 87

Ruby Array

map { |item| block } => new_ary

Answer 87

return a new array containing the values returned by the block, which is invoked once for each element of self

Question 88

Ruby Array

permutation(n) => Enumerator

permutation(n) { |p| block } => ary

Answer 88

yield all permutations of length n of the elements of self, then return the array itself

Question 89

Ruby Array

pop => obj or nil

pop(n) => new_ary

Answer 89

remove the last n elements of self and return them

Question 90

Ruby Array

product(other_ary, …) => new_ary

Answer 90

return an array of all combinations of elements of all arrays

Question 91

Ruby Array

push(obj, …) => ary

Answer 91

append - push the given object(s) on to the end of self, returning the array itself

Question 92

Ruby Array

rassoc(obj) => element or nil

Answer 92

search through self whose elements are also arrays; compare obj with the second element of each contained array; return the first contained array that matches obj

Question 93

Ruby Array

repeated_combinations(n) => Enumerator

Answer 93

yield all repeated combinations of length n of elements of self then returns the array itself

Question 94

Ruby Array

repeated_permutation(n) => Enumerator

Answer 94

yield all repeated permuations of length n of the elements of self, then return the array itself

Question 95

Ruby Array

reverse => new_ary

Answer 95

return a new array containing self’s elements in reverse order

Question 96

Ruby Array

reverse_each { |item| block } => ary

Answer 96

same as Array#each but traverses self in reverse order

Question 97

Ruby Array

rindex(obj) => int or nil

rindex(obj) { |item| block } => int or nil

Answer 97

return the index of the last element in self that == obj; if a block is given, return the index of the last element in self for which the block returns true

Question 98

Ruby Array

rotate(count=1) => new_ary

Answer 98

return a new array by rotating self so that the element at count is the first element of the new array

Question 99

Ruby Array

sample => obj

sample(n) => new_ary

Answer 99

choose a random element or n random elements from self

Question 100

Ruby Array

select { |item| block } => new_ary

Answer 100

return a new array containing all elements of self for which the block returns a true value

Question 101

Ruby Array

shift => obj

Answer 101

remove the first element of self and returns it (shifting all other elements down by one); returns nil if empty

Question 102

Ruby Array

shuffle => new_ary

Answer 102

return a new array with the elements of self shuffled

Question 103

Ruby Array

sort => new_ary

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

Answer 103

return a new array created by sorting self; comparisons done using ; if a block is given, it must implement a comparison between a and b and return a negative integer if a

Question 104

Ruby Array

take(n) => new_ary

Answer 104

return the first n elements of self

Question 105

Ruby Array

take_while { |obj| block } => new_ary

Answer 105

pass elements of self to the block until the block returns nil or false; returns an array of all prior elements

Question 106

Ruby Array

transpose => new_ary

Answer 106

assume that self is an array of arrays and transposes rows and columns

Question 107

Ruby Array

uniq => new_ary

uniq { |item| block } => new_ary

Answer 107

return a new array by removing duplicate values in self; if a block is given, use the return value of the block for comparison

Question 108

Ruby Array

unshift(obj, …) => ary

Answer 108

prepend obj to the front of self, moving other elements upwards

Question 109

Ruby Array

zip(arg, …) => new_ary

zip(arg, …) { |arr| block } => nil

Answer 109

convert any arguments to arrays, then merges elements of self with corresponding elements from each argument; if a block is given, it’s invoked for each output array, otherwise an array of arrays is returned

Question 110

Ruby Array

ary | other_ary => new_ary

Answer 110

set union - return a new array by joining ary and other_ary, excluding any duplicates and preserving the order from the original array