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