Merging hashes and keys gets both old and new values
Imagine I have an array like this
array = [4,"hello",[[3],:d,7,[:a,"seven"]]]
class Array
def deep_collect_by_elem_type_as_hash()
e = {}
self.each(){|x|
if x.is_a?(Array)
e.merge(x.deep_collect_by_elem_type_as_hash)
end
if !x.is_a?(Array)
if e.has_key?(x.class)
e[x.class]<<x
else
e[x.class] = [x]
end
end
}
return e
end
I want all of my arrays to create a hash that has keys containing the different classes that are in my array. Their values will be valid elements for each class.
So it will look like this:
{Fixnum=>[4, 3, 7], String=>["hello", "seven"], Symbol=>[:d, :a]}
I want to solve all of this without using anti-aliasing, but doing it recruitingly. A flat solution might look like this:
def deep_collect_by_elem_type_as_hash1()
e = {}
flat= self.flatten()
flat.each(){|x|
if e.has_key?(x.class)
e[x.class]<<x
else
e[x.class] = [x]
end
}
return e
end
For those wondering why I don't want to use anti-aliasing: I still have problems fully understanding how to implement recursive methods and so this is a question that will help me understand better.
I think I somehow need to implement a merge with a block, but I can't figure out the correct block. merge(x.deep_collect_by_elem_type_as_hash(){|k,v1,v2| help}
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Here we go:
a = [4,"hello",[[3],:d,7,[:a,"seven"]]]
def stuff(a)
res = {}
a.each do |e|
if e.is_a?(Array)
stuff(e).each do |k,v|
res[k] ||= []
v.each {|x| res[k] << x}
end
else
k = e.class
res[k] ||= []
res[k] << e
end
end
res
end
puts stuff(a).inspect
if you need to open and expand an array, you can do something line by line:
class Array
def stuff(a = self)
...
end
end
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You can do it like this:
def group_by_class(arr, h = Hash.new { |h,k| h[k] = [] })
arr.each { |e| e.is_a?(Array) ? group_by_class(e,h) : h[e.class] << e }
h
end
array = [4,"hello",[[3],:d,7,[:a,"seven"]]]
group_by_class(array)
#=> {Fixnum=>[4, 3, 7], String=>["hello", "seven"], Symbol=>[:d, :a]}
array = [4,"hello",[[3],:d,7,[:a,"seven",["b",9,[:e,["cat", {a: 0}, 5]]]]]]
group_by_class(array)
#=> {Fixnum=>[4, 3, 7, 9, 5], String=>["hello", "seven", "b", "cat"],
# Symbol=>[:d, :a, :e], Hash=>[{:a=>0}]}
You can also write:
def group_by_class(arr)
arr.each { |e| e.is_a?(Array) ? group_by_class(e) : @h[e.class] << e }
end
@h = Hash.new { |h,k| h[k] = [] }
group_by_class(array)
@h
#=> {Fixnum=>[4, 3, 7, 9, 5], String=>["hello", "seven", "b", "cat"],
# Symbol=>[:d, :a, :e], Hash=>[{:a=>0}]}
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