Class: Array

Inherits:
Object show all
Extended by:
Fr::Monad, Fr::Monoid
Defined in:
lib/fr/array.rb

Selection collapse

Filtering collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Fr::Monoid

filter, guard, sum

Methods included from Fr::Monad

applyM, composeM, filterM, foldM, forM, join, liftM, mapM, sequence, unlessM, whenM, zipM

Methods included from Fr::Functor

#void

Class Method Details

.bind(x, &f) ⇒ Object 



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# File 'lib/fr/monad/array.rb', line 18

def bind(x, &f)
  x.map(&f).inject([], &:concat)
end

.plus(a, b) ⇒ Object

Array a -> Array a -> Array a



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# File 'lib/fr/monoid/array.rb', line 10

def plus(a, b)
  a + b
end

.run(computation) ⇒ Object

Evaluators



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# File 'lib/fr/monad/array.rb', line 7

def run(computation)
  computation
end

.unfold(seed) ⇒ Object

First generated element is first in Array



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# File 'lib/fr/unfold.rb', line 3

def unfold(seed, &block)
  m = yield(seed)
  m.fold([]){|(item, seed)| [item] + unfold(seed, &block) }
end

.unfoldR(seed) ⇒ Object

First generated element is last in Array



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# File 'lib/fr/unfold.rb', line 21

def unfoldR(seed, &block)
  m = yield(seed)
  m.fold([]){|(item, seed)| unfold(seed, &block) + [item] }
end

.unit(value) ⇒ Object

Combinators



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# File 'lib/fr/monad/array.rb', line 14

def unit(value)
  [value]
end

.zero ⇒ Object

Array a



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# File 'lib/fr/monoid/array.rb', line 5

def zero
  []
end

Instance Method Details

#defined_at?(n) ⇒ Boolean

True if ‘#at` is defined for the given `n`

Examples:

[1, 2, 3].defined_at?(0)    #=> true
[].defined_at?(0)           #=> false



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# File 'lib/fr/array.rb', line 20

def defined_at?(n)
  n < length and -n <= length
end

#drop(n) ⇒ Array

Select all elements except the first ‘n` ones.

Examples:

[1, 2, 3].drop(1)   #=> [2, 3]
[1, 3, 3].drop(2)   #=> [3]
[].drop(10)         #=> []

Raises:

  • (ArgumentError) 


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# File 'lib/fr/array.rb', line 61

def drop(n)
  raise ArgumentError, "n cannot be negative" if n < 0
  slice(n..-1) or []
end

#drop_until(&block) ⇒ Array

Drops the longest prefix of elements that do not satisfy the predicate.



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# File 'lib/fr/array.rb', line 111

def drop_until(&block)
  # This is in tail call form
  unless empty? or yield(head)
    tail.drop_until(&block)
  else
    self
  end
end

#drop_while(&block) ⇒ Array

Drops the longest prefix of elements that satisfy the predicate.



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# File 'lib/fr/array.rb', line 99

def drop_while(&block)
  # This is in tail call form
  if not empty? and yield(head)
    tail.drop_while(&block)
  else
    self
  end
end

#head ⇒ Object

Return the first item. Raises an ‘IndexError` if the Array is `empty?`.

Examples:

[1, 2, 3].head  #=> 1

Raises:

  • (IndexError) 


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# File 'lib/fr/array.rb', line 8

def head
  raise IndexError, "head of empty list" if empty?
  x, = self
  x
end

#init(n = 1) ⇒ Array

Selects all elements except the last ‘n` ones.

Examples:

[1, 2, 3].init      #=> [1, 2]
[1, 2, 3].init(2)   #=> [1]
[].tail             #=> []

Raises:

  • (ArgumentError) 


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# File 'lib/fr/array.rb', line 48

def init(n = 1)
  raise ArgumentError, "n cannot be negative" if n < 0
  slice(0..-(n + 1)) or []
end

#split_at(n) ⇒ (Array, Array)

Split the array in two at the given position.

Examples:

[1, 2, 3].split_at(2)   #=> [[1,2], [3]]
[1, 2, 3].split_at(0)   #=> [[], [1,2,3]]



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# File 'lib/fr/array.rb', line 85

def split_at(n)
  n = length + n if n < 0
  return take(n), drop(n)
end

#split_until(&block) ⇒ (Array, Array)

Splits the array into prefix/suffix pair according to the predicate.



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# File 'lib/fr/array.rb', line 147

def split_until(&block)
  prefix = take_while(&block)
  suffix = drop(prefix.length)
  return prefix, suffix
end

#split_when(&block) ⇒ (Array, Array)

Splits the array into prefix/suffix pair according to the predicate.



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# File 'lib/fr/array.rb', line 156

def split_when(&block)
  prefix = take_until(&block)
  suffix = drop(prefix.length)
  return prefix, suffix
end

#tail ⇒ Array

Selects all elements except the first.

Examples:

[1, 2, 3].tail  #=> [2, 3]
[1].tail        #=> []
[].tail         #=> []



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# File 'lib/fr/array.rb', line 35

def tail
  _, *xs = self
  xs
end

#take(n) ⇒ Array

Select the first ‘n` elements.

Examples:

[1, 2, 3].take(2)  #=> [1, 2]
[1, 2, 3].take(0)  #=> []

Raises:

  • (ArgumentError) 


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# File 'lib/fr/array.rb', line 73

def take(n)
  raise ArgumentError, "n cannot be negative" if n < 0
  slice(0, n) or []
end

#take_until(accumulator = [], &block) ⇒ Array

Takes the longest prefix of elements that do not satisfy the predicate.



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# File 'lib/fr/array.rb', line 135

def take_until(accumulator = [], &block)
  # This is in tail call form
  unless empty? or yield(head)
    tail.take_until(head.snoc(accumulator), &block)
  else
    accumulator
  end
end

#take_while(accumulator = [], &block) ⇒ Array

Takes the longest prefix of elements that satisfy the predicate.



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# File 'lib/fr/array.rb', line 123

def take_while(accumulator = [], &block)
  # This is in tail call form
  if not empty? and yield(head)
    tail.take_while(head.snoc(accumulator), &block)
  else
    accumulator
  end
end