Sparse matrix 2

Ruby
1

Class SparseVector
attr_reader :vector

def initialize(h = {})
    @vector = Hash.new(0)
    @vector = @vector.merge!(h)
end

def [](i)
    @vector[i]
end

def to_s
    @vector.to_s
end

end

class SparseMatrix

attr_reader :matrix

def initialize(h = {})
    @matrix = Hash.new({})
    for k in h.keys do
        @matrix[k] = if h[k].is_a? SparseVector
        h[k]
    else
        @matrix[k] = SparseVector.new(h[k])
    end
end

end

def [](i)
    @matrix[i]
end

def col(j)
    c = {}
    for r in @matrix.keys do
        c[r] = @matrix[r].vector[j] if

@matrix[r].vector.keys.include? j
end
SparseVector.new c
end
end

hsh = SparseMatrix.new 1 => {1 => 33, 2 => 44, 3 => 55}, 2 => {1 => 66,
3 => 77}
puts hsh[1][3]
puts hsh.col(2)

That’s the code I have, I need to know if I can if I can get the indexes
of the hash looping through the hash.
I’ve tried using each-do, but i couldn’t make it work.
I need to do this so that I can operate with Sparse Matrices and Dense
Matrices.

2

On Tue, Nov 19, 2013 at 10:59 PM, aaron v. [email protected] wrote:

end
def initialize(h = {})
def [](i)
end

end

hsh = SparseMatrix.new 1 => {1 => 33, 2 => 44, 3 => 55}, 2 => {1 => 66,
3 => 77}
puts hsh[1][3]
puts hsh.col(2)

That’s the code I have, I need to know if I can if I can get the indexes
of the hash looping through the hash.
I’ve tried using each-do, but i couldn’t make it work.

Since you are nesting Hashes you need a recursive approach at finding
all indexes.

def each_index
return enum_for(each_index) unless block_given?

each_entry(@matrix, []) {|i,| yield i}
self
end

def each_entry(hash, index_prefix, &b)
hash.each do |key, value|
idx = index_prefix + [key]

if Hash === value
  each_entry(value, idx, &b)
else
  yield idx, value
fi

end
end

Kind regards

robert