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Contents
module Dry
module Monads
# Advanced tranformations.
module Transformer
# Lifts a block/proc over the 2-level nested structure.
# This is essentially fmap . fmap (. is the function composition
# operator from Haskell) or the functor instance for
# a two-level monadic structure like List Either.
#
# @example
# List[Right(1), Left(1)].fmap2 { |x| x + 1 } # => List[Right(2), Left(1)]
# Right(None).fmap2 { |x| x + 1 } # => Right(None)
#
# @param args [Array<Object>] arguments will be passed to the block or the proc
# @return [Object] some monadic value
def fmap2(*args)
if block_given?
fmap { |a| a.fmap { |b| yield(b, *args) } }
else
func, *rest = args
fmap { |a| a.fmap { |b| func.(b, *rest) } }
end
end
# Lifts a block/proc over the 3-level nested structure.
#
# @example
# List[Right(Some(1)), Left(Some(1))].fmap3 { |x| x + 1 } # => List[Right(Some(2)), Left(Some(1))]
# Right(None).fmap3 { |x| x + 1 } # => Right(None)
#
# @param args [Array<Object>] arguments will be passed to the block or the proc
# @return [Object] some monadic value
def fmap3(*args)
if block_given?
fmap { |a| a.fmap { |b| b.fmap { |c| yield(c, *args) } } }
else
func, *rest = args
fmap { |a| a.fmap { |b| b.fmap { |c| func.(c, *rest) } } }
end
end
end
end
end
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13 entries across 13 versions & 1 rubygems