/
named_tuple.cr
567 lines (527 loc) · 13.7 KB
/
named_tuple.cr
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# A named tuple is a fixed-size, immutable, stack-allocated mapping
# of a fixed set of keys to values.
#
# You can think of a `NamedTuple` as an immutable `Hash` whose keys (which
# are of type `Symbol`), and the types for each key, are known at compile time.
#
# A named tuple can be created with a named tuple literal:
#
# ```
# language = {name: "Crystal", year: 2011} # NamedTuple(name: String, year: Int32)
#
# language[:name] # => "Crystal"
# language[:year] # => 2011
# language[:other] # compile time error
# ```
#
# The compiler knows what types are in each key, so when indexing a named tuple
# with a symbol literal the compiler will return the value for that key and
# with the expected type, like in the above snippet. Indexing with a symbol
# literal for which there's no key will give a compile-time error.
#
# Indexing with a symbol that is only known at runtime will return
# a value whose type is the union of all the types in the named tuple,
# and might raise `KeyError`.
struct NamedTuple
# Creates a named tuple that will contain the given arguments.
#
# This method is useful in macros and generic code because with it you can
# creates empty named tuples, something that you can't do with a tuple literal.
#
# ```
# NamedTuple.new(name: "Crystal", year: 2011) #=> {name: "Crystal", year: 2011}
# NamedTuple.new # => {}
# {} # syntax error
# ```
def self.new(**options : **T)
options
end
# Creates a named tuple from the given hash, with elements casted to the given types.
# Here the Int32 | String union is cast to Int32.
#
# ```
# num_or_str = 42.as(Int32 | String)
# NamedTuple(name: String, val: Int32).from({"name" => "number", "val" => num_or_str}) # => {name: "number", val: 42}
#
# num_or_str = "a string".as(Int32 | String)
# NamedTuple(name: String, val: Int32).from({"name" => "number", "val" => num_or_str}) # raises TypeCastError (cast from String to Int32 failed)
# ```
# See also: `#from`.
def self.from(hash : Hash) : self
{% begin %}
NamedTuple.new(**{{T}}).from(hash)
{% end %}
end
# Expects to be called on a named tuple whose values are types, creates a tuple from the given hash,
# with types casted appropriately. The hash keys must be either symbols or strings.
#
# This allows you to easily pass a hash as individual named arguments to a method.
#
# ```
# require "json"
#
# def speak_about(thing : String, n : Int64)
# "I see #{n} #{thing}s"
# end
#
# hash = JSON.parse(%({"thing": "world", "n": 2})).as_h # hash : Hash(String, JSON::Any)
# hash = hash.transform_values(&.raw) # hash : Hash(String, JSON::Any::Type)
#
# speak_about(**{thing: String, n: Int64}.from(hash)) # => "I see 2 worlds"
# ```
def from(hash : Hash)
if size != hash.size
raise ArgumentError.new("Expected a hash with #{size} keys but one with #{hash.size} keys was given.")
end
{% begin %}
NamedTuple.new(
{% for key, value in T %}
{{key.stringify}}: self[{{key.symbolize}}].cast(hash.fetch({{key.symbolize}}) { hash["{{key}}"] }),
{% end %}
)
{% end %}
end
# Returns the value for the given *key*, if there's such key, otherwise raises `KeyError`.
#
# ```
# tuple = {name: "Crystal", year: 2011}
#
# key = :name
# tuple[key] # => "Crystal"
#
# key = "year"
# tuple[key] # => 2011
#
# key = :other
# tuple[key] # raises KeyError
# ```
def [](key : Symbol | String)
fetch(key) { raise KeyError.new "Missing named tuple key: #{key.inspect}" }
end
# Returns the value for the given *key*, if there's such key, otherwise returns `nil`.
#
# ```
# tuple = {name: "Crystal", year: 2011}
#
# key = :name
# tuple[key]? # => "Crystal"
#
# key = "year"
# tuple[key] # => 2011
#
# key = :other
# tuple[key]? # => nil
# ```
def []?(key : Symbol | String)
fetch(key, nil)
end
# Traverses the depth of a structure and returns the value.
# Returns `nil` if not found.
#
# ```
# h = {a: {b: [10, 20, 30]}}
# h.dig? "a", "b" # => [10, 20, 30]
# h.dig? "a", "b", "c", "d", "e" # => nil
# ```
def dig?(key : Symbol | String, *subkeys)
if (value = self[key]?) && value.responds_to?(:dig?)
value.dig?(*subkeys)
end
end
# :nodoc:
def dig?(key : Symbol | String)
self[key]?
end
# Traverses the depth of a structure and returns the value, otherwise
# raises `KeyError`.
#
# ```
# h = {a: {b: [10, 20, 30]}}
# h.dig "a", "b" # => [10, 20, 30]
# h.dig "a", "b", "c", "d", "e" # raises KeyError
# ```
def dig(key : Symbol | String, *subkeys)
if (value = self[key]) && value.responds_to?(:dig)
return value.dig(*subkeys)
end
raise KeyError.new "NamedTuple value not diggable for key: #{key.inspect}"
end
# :nodoc:
def dig(key : Symbol | String)
self[key]
end
# Returns the value for the given *key*, if there's such key, otherwise returns *default_value*.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.fetch(:name, "Unknown") # => "Crystal"
# tuple.fetch("year", 0) # => 2011
# tuple.fetch(:other, 0) # => 0
# ```
def fetch(key : Symbol | String, default_value)
fetch(key) { default_value }
end
# Returns the value for the given *key*, if there's such key, otherwise the value returned by the block.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.fetch(:name) { "Unknown" } # => "Crystal"
# tuple.fetch(:other) { 0 } # => 0
# ```
def fetch(key : Symbol, &block)
{% for key in T %}
return self[{{key.symbolize}}] if {{key.symbolize}} == key
{% end %}
yield
end
# Returns the value for the given *key*, if there's such key, otherwise the value returned by the block.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.fetch("name") { "Unknown" } # => "Crystal"
# tuple.fetch("other") { 0 } # => 0
# ```
def fetch(key : String, &block)
{% for key in T %}
return self[{{key.symbolize}}] if {{key.stringify}} == key
{% end %}
yield
end
# Merges two named tuples into one, returning a new named tuple.
# If a key is defined in both tuples, the value and its type is used from *other*.
#
# ```
# a = {foo: "Hello", bar: "Old"}
# b = {bar: "New", baz: "Bye"}
# a.merge(b) # => {foo: "Hello", bar: "New", baz: "Bye"}
# ```
def merge(other : NamedTuple)
merge(**other)
end
# ditto
def merge(**other : **U) forall U
{% begin %}
{
{% for k in T %} {% unless U.keys.includes?(k) %} {{k.stringify}}: self[{{k.symbolize}}],{% end %} {% end %}
{% for k in U %} {{k.stringify}}: other[{{k.symbolize}}], {% end %}
}
{% end %}
end
# Returns a hash value based on this name tuple's size, keys and values.
#
# See also: `Object#hash`.
# See `Object#hash(hasher)`
def hash(hasher)
{% for key in T.keys.sort %}
hasher = {{key.symbolize}}.hash(hasher)
hasher = self[{{key.symbolize}}].hash(hasher)
{% end %}
hasher
end
# Returns the types of this named tuple type.
#
# ```
# tuple = {a: 1, b: "hello", c: 'x'}
# tuple.class.types # => {a: Int32, b: String, c: Char}
# ```
def self.types
NamedTuple.new(**{{T}})
end
# Same as `to_s`.
def inspect
to_s
end
# Returns a `Tuple` of symbols with the keys in this named tuple.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.keys # => {:name, :year}
# ```
def keys
{% begin %}
Tuple.new(
{% for key in T %}
{{key.symbolize}},
{% end %}
)
{% end %}
end
protected def sorted_keys
{% begin %}
Tuple.new(
{% for key in T.keys.sort %}
{{key.symbolize}},
{% end %}
)
{% end %}
end
# Returns a `Tuple` with the values in this named tuple.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.values # => {"Crystal", 2011}
# ```
def values
{% begin %}
Tuple.new(
{% for key in T %}
self[{{key.symbolize}}],
{% end %}
)
{% end %}
end
# Returns `true` if this named tuple has the given *key*, `false` otherwise.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.has_key?(:name) # => true
# tuple.has_key?(:other) # => false
# ```
def has_key?(key : Symbol) : Bool
{% for key in T %}
return true if {{key.symbolize}} == key
{% end %}
false
end
# ditto
def has_key?(key : String) : Bool
{% for key in T %}
return true if {{key.stringify}} == key
{% end %}
false
end
# Appends a string representation of this named tuple to the given `IO`.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.to_s # => %({name: "Crystal", year: 2011})
# ```
def to_s(io)
io << '{'
{% for key, value, i in T %}
{% if i > 0 %}
io << ", "
{% end %}
key = {{key.stringify}}
if Symbol.needs_quotes?(key)
key.inspect(io)
else
io << key
end
io << ": "
self[{{key.symbolize}}].inspect(io)
{% end %}
io << '}'
end
def pretty_print(pp)
pp.surround("{", "}", left_break: nil, right_break: nil) do
{% for key, value, i in T %}
{% if i > 0 %}
pp.comma
{% end %}
pp.group do
key = {{key.stringify}}
if Symbol.needs_quotes?(key)
pp.text key.inspect
else
pp.text key
end
pp.text ": "
pp.nest do
pp.breakable ""
self[{{key.symbolize}}].pretty_print(pp)
end
end
{% end %}
end
end
# Yields each key and value in this named tuple.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.each do |key, value|
# puts "#{key} = #{value}"
# end
# ```
#
# Output:
#
# ```text
# name = Crystal
# year = 2011
# ```
def each : Nil
{% for key in T %}
yield {{key.symbolize}}, self[{{key.symbolize}}]
{% end %}
end
# Yields each key in this named tuple.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.each_key do |key|
# puts key
# end
# ```
#
# Output:
#
# ```text
# name
# year
# ```
def each_key : Nil
{% for key in T %}
yield {{key.symbolize}}
{% end %}
end
# Yields each value in this named tuple.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.each_value do |value|
# puts value
# end
# ```
#
# Output:
#
# ```text
# Crystal
# 2011
# ```
def each_value : Nil
{% for key in T %}
yield self[{{key.symbolize}}]
{% end %}
end
# Yields each key and value, together with an index starting at *offset*, in this named tuple.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.each_with_index do |key, value, i|
# puts "#{i + 1}) #{key} = #{value}"
# end
# ```
#
# Output:
#
# ```text
# 1) name = Crystal
# 2) year = 2011
# ```
def each_with_index(offset = 0)
i = offset
each do |key, value|
yield key, value, i
i += 1
end
end
# Returns an `Array` populated with the results of each iteration in the given block,
# which is given each key and value in this named tuple.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.map { |k, v| "#{k}: #{v}" } # => ["name: Crystal", "year: 2011"]
# ```
def map
array = Array(typeof(yield first_key_internal, first_value_internal)).new(size)
each do |k, v|
array.push yield k, v
end
array
end
# Returns a new `Array` of tuples populated with each key-value pair.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.to_a # => [{:name, "Crystal"}, {:year, 2011}]
# ```
def to_a
ary = Array({typeof(first_key_internal), typeof(first_value_internal)}).new(size)
each do |key, value|
ary << {key.as(typeof(first_key_internal)), value.as(typeof(first_value_internal))}
end
ary
end
# Returns a `Hash` with the keys and values in this named tuple.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.to_h # => {:name => "Crystal", :year => 2011}
# ```
def to_h
{% if T.size == 0 %}
{} of NoReturn => NoReturn
{% else %}
{
{% for key in T %}
{{key.symbolize}} => self[{{key.symbolize}}],
{% end %}
}
{% end %}
end
# Returns the number of elements in this named tuple.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.size # => 2
# ```
def size
{{T.size}}
end
# Returns `true` if this named tuple is empty.
#
# ```
# tuple = {name: "Crystal", year: 2011}
# tuple.empty? # => false
# ```
def empty?
size == 0
end
# Returns `true` if this tuple has the same keys as *other*, and values
# for each key are the same in `self` and *other*.
#
# ```
# tuple1 = {name: "Crystal", year: 2011}
# tuple2 = {year: 2011, name: "Crystal"}
# tuple3 = {name: "Crystal", year: 2012}
# tuple4 = {name: "Crystal", year: 2011.0}
#
# tuple1 == tuple2 # => true
# tuple1 == tuple3 # => false
# tuple1 == tuple4 # => true
# ```
def ==(other : self)
{% for key in T %}
return false unless self[{{key.symbolize}}] == other[{{key.symbolize}}]
{% end %}
true
end
# ditto
def ==(other : NamedTuple)
return false unless sorted_keys == other.sorted_keys
{% for key in T %}
return false unless self[{{key.symbolize}}] == other[{{key.symbolize}}]?
{% end %}
return true
end
# Returns a named tuple with the same keys but with cloned values, using the `clone` method.
def clone
{% begin %}
{
{% for key in T %}
{{key.stringify}}: self[{{key.symbolize}}].clone,
{% end %}
}
{% end %}
end
private def first_key_internal
i = 0
keys[i]
end
private def first_value_internal
i = 0
values[i]
end
end