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|
class Hash
##
# call-seq:
# hsh.merge!(other_hash) -> hsh
# hsh.merge!(other_hash){|key, oldval, newval| block} -> hsh
#
# Adds the contents of _other_hash_ to _hsh_. If no block is specified,
# entries with duplicate keys are overwritten with the values from
# _other_hash_, otherwise the value of each duplicate key is determined by
# calling the block with the key, its value in _hsh_ and its value in
# _other_hash_.
#
# h1 = { "a" => 100, "b" => 200 }
# h2 = { "b" => 254, "c" => 300 }
# h1.merge!(h2) #=> {"a"=>100, "b"=>254, "c"=>300}
#
# h1 = { "a" => 100, "b" => 200 }
# h2 = { "b" => 254, "c" => 300 }
# h1.merge!(h2) { |key, v1, v2| v1 }
# #=> {"a"=>100, "b"=>200, "c"=>300}
#
def merge!(other, &block)
raise "can't convert argument into Hash" unless other.respond_to?(:to_hash)
if block
other.each_key{|k|
self[k] = (self.has_key?(k))? block.call(k, self[k], other[k]): other[k]
}
else
other.each_key{|k| self[k] = other[k]}
end
self
end
alias each_pair each
alias update merge!
##
# call-seq:
# hsh.fetch(key [, default] ) -> obj
# hsh.fetch(key) {| key | block } -> obj
#
# Returns a value from the hash for the given key. If the key can't be
# found, there are several options: With no other arguments, it will
# raise an <code>KeyError</code> exception; if <i>default</i> is
# given, then that will be returned; if the optional code block is
# specified, then that will be run and its result returned.
#
# h = { "a" => 100, "b" => 200 }
# h.fetch("a") #=> 100
# h.fetch("z", "go fish") #=> "go fish"
# h.fetch("z") { |el| "go fish, #{el}"} #=> "go fish, z"
#
# The following example shows that an exception is raised if the key
# is not found and a default value is not supplied.
#
# h = { "a" => 100, "b" => 200 }
# h.fetch("z")
#
# <em>produces:</em>
#
# prog.rb:2:in `fetch': key not found (KeyError)
# from prog.rb:2
#
def fetch(key, none=NONE, &block)
unless self.key?(key)
if block
block.call
elsif none != NONE
none
else
raise RuntimeError, "Key not found: #{key}"
end
else
self[key]
end
end
##
# call-seq:
# hsh.delete_if {| key, value | block } -> hsh
# hsh.delete_if -> an_enumerator
#
# Deletes every key-value pair from <i>hsh</i> for which <i>block</i>
# evaluates to <code>true</code>.
#
# If no block is given, an enumerator is returned instead.
#
# h = { "a" => 100, "b" => 200, "c" => 300 }
# h.delete_if {|key, value| key >= "b" } #=> {"a"=>100}
#
def delete_if(&block)
return to_enum :delete_if unless block_given?
self.each do |k, v|
self.delete(k) if block.call(k, v)
end
self
end
end
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