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module Backports
# Helper method to coerce a value into a specific class.
# Raises a TypeError if the coercion fails or the returned value
# is not of the right class.
# (from Rubinius)
def self.coerce_to(obj, cls, meth)
return obj if obj.kind_of?(cls)
begin
ret = obj.__send__(meth)
rescue Exception => e
raise TypeError, "Coercion error: #{obj.inspect}.#{meth} => #{cls} failed:\n" \
"(#{e.message})"
end
raise TypeError, "Coercion error: obj.#{meth} did NOT return a #{cls} (was #{ret.class})" unless ret.kind_of? cls
ret
end
def self.coerce_to_int(obj)
coerce_to(obj, Integer, :to_int)
end
def self.coerce_to_ary(obj)
coerce_to(obj, Array, :to_ary)
end
def self.coerce_to_str(obj)
coerce_to(obj, String, :to_str)
end
def self.coerce_to_hash(obj)
coerce_to(obj, Hash, :to_hash)
end
def self.coerce_to_options(obj, *options)
hash = coerce_to_hash(obj)
hash.values_at(*options)
end
def self.coerce_to_option(obj, option)
coerce_to_options(obj, option)[0]
end
def self.is_array?(obj)
coerce_to(obj, Array, :to_ary) if obj.respond_to? :to_ary
end
def self.try_convert(obj, cls, meth)
return obj if obj.kind_of?(cls)
return nil unless obj.respond_to?(meth)
ret = obj.__send__(meth)
raise TypeError, "Coercion error: obj.#{meth} did NOT return a #{cls} (was #{ret.class})" unless ret.nil? || ret.kind_of?(cls)
ret
end
# Checks for a failed comparison (in which case it throws an ArgumentError)
# Additionally, it maps any negative value to -1 and any positive value to +1
# (from Rubinius)
def self.coerce_to_comparison(a, b, cmp = (a <=> b))
raise ArgumentError, "comparison of #{a} with #{b} failed" if cmp.nil?
return 1 if cmp > 0
return -1 if cmp < 0
0
end
# Used internally to make it easy to deal with optional arguments
# (from Rubinius)
Undefined = Object.new
end
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