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|
# frozen_string_literal: true
module Unparser
module RequireBlock
private
# Raise error unless block is provided
#
# @raise [MissingBlockError]
# if no block is given
#
# @return [self]
def require_block
fail LocalJumpError unless block_given?
self
end
end # RequireBLock
class Either
include(
Adamantium,
Concord.new(:value),
RequireBlock
)
# Execute block and wrap error in left
#
# @param [Class<Exception>] exception
#
# @return [Either<Exception, Object>]
def self.wrap_error(*exceptions)
Right.new(yield)
rescue *exceptions => error
Left.new(error)
end
# Test for left constructor
#
# @return [Boolean]
def left?
instance_of?(Left)
end
# Test for right constructor
#
# @return [Boolean]
def right?
instance_of?(Right)
end
class Left < self
# Evaluate functor block
#
# @return [Either::Left<Object>]
def fmap(&block)
require_block(&block)
end
# Evaluate applicative block
#
# @return [Either::Left<Object>]
def bind(&block)
require_block(&block)
end
# Unwrap value from left
#
# @return [Object]
def from_left
value
end
# Unwrap value from right
#
# @return [Object]
#
def from_right
if block_given?
yield(value)
else
fail "Expected right value, got #{inspect}"
end
end
# Map over left value
#
# @return [Either::Right<Object>]
def lmap
Left.new(yield(value))
end
# Evaluate left side of branch
#
# @param [#call] left
# @param [#call] _right
def either(left, _right)
left.call(value)
end
end # Left
class Right < self
# Evaluate functor block
#
# @return [Either::Right<Object>]
def fmap
Right.new(yield(value))
end
# Evaluate applicative block
#
# @return [Either<Object>]
def bind
yield(value)
end
# Unwrap value from left
#
# @return [Object]
#
def from_left
if block_given?
yield(value)
else
fail "Expected left value, got #{inspect}"
end
end
# Unwrap value from right
#
# @return [Object]
def from_right
value
end
# Map over left value
#
# @return [Either::Right<Object>]
def lmap(&block)
require_block(&block)
end
# Evaluate right side of branch
#
# @param [#call] _left
# @param [#call] right
def either(_left, right)
right.call(value)
end
end # Right
end # Either
end # Unparser
|
