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Implement Matrix#rotate_entries #20

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Implement Matrix#rotate_entries #20

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68a3aba
Implement Matrix#rotate_entries (#19)
fwolfst Dec 21, 2020
cb087a7
Let Matrix#rotate_entries handle empty Matrices (#19)
fwolfst Dec 22, 2020
3b9cebb
Handle positive integers in Matrix#rotate_entries
fwolfst Dec 22, 2020
0c4ef4a
Test Matrix#rotate_entries with negative numerics.
fwolfst Dec 22, 2020
04219c6
Add example to Matrix#rotate_entries doc.
fwolfst Dec 22, 2020
6dd93ee
Make rotate_entries argument positional argument
fwolfst Dec 23, 2020
8cec6e7
Simplify integer handling in Matrix#rotate_entries
fwolfst Dec 23, 2020
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52 changes: 52 additions & 0 deletions lib/matrix.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -1435,6 +1435,58 @@ def rank_e
rank
end

#
# Returns a new matrix where elements are rotated.
# The +quarter_turns+ option defines the direction of the rotation (defaults
# to :clockwise):
# * :clockwise: "turn right" - first row becomes last column
# * :counter_clockwise: "turn left" - first row becomes first column
# (but with elements in reverse order)
# * :half_turn: first row becomes last row, elements in reverse order
#
# m = Matrix[ [1, 2], [3, 4] ]
# r = m.rotate_entries(:clockwise)
# # => Matrix[[3, 1], [4, 2]]
#
def rotate_entries(quarter_turns=:clockwise)
if quarter_turns.is_a? Integer
quarter_turns = case quarter_turns % 4
when 0
:dup
when 1
:clockwise
when 2
:half_turn
when 3
:counter_clockwise
end
end

if empty?
case quarter_turns
when :clockwise, :counter_clockwise
return Matrix.empty(column_count, row_count)
when :half_turn, :dup
return Matrix.empty(row_count, column_count)
else
raise ArgumentError, "expected #{quarter_turns.inspect} to be one of :clockwise, :counter_clockwise, :half_turn or an integer (assuming clockwise rotation)"
end
end

case quarter_turns
when :dup
self.dup
when :clockwise
Matrix[*column_vectors.map{|c| c.to_a.reverse}]
when :counter_clockwise
Matrix[*column_vectors.map{|c| c}.reverse]
when :half_turn
Matrix[*row_vectors.map{|c| c.to_a.reverse}.reverse]
else
raise ArgumentError, "expected #{quarter_turns.inspect} to be one of :clockwise, :counter_clockwise, :half_turn or an integer (assuming clockwise rotation)"
end
end

# Returns a matrix with entries rounded to the given precision
# (see Float#round)
#
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56 changes: 56 additions & 0 deletions test/matrix/test_matrix.rb
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Expand Up @@ -821,4 +821,60 @@ def test_ractor
end.take
assert_same obj1, obj2
end if defined?(Ractor)

def test_rotate_with_symbol
assert_equal(Matrix[[4, 1], [5, 2], [6, 3]], @m1.rotate_entries)
assert_equal(@m1.rotate_entries, @m1.rotate_entries(:clockwise))
assert_equal(Matrix[[4, 1], [5, 2], [6, 3]],
@m1.rotate_entries(:clockwise))
assert_equal(Matrix[[3, 6], [2, 5], [1, 4]],
@m1.rotate_entries(:counter_clockwise))
assert_equal(Matrix[[6, 5, 4], [3, 2, 1]],
@m1.rotate_entries(:half_turn))
assert_equal(Matrix[[6, 5, 4], [3, 2, 1]],
@m1.rotate_entries(:half_turn))
assert_equal(Matrix.empty(0,2),
@e1.rotate_entries(:clockwise))
assert_equal(Matrix.empty(0,2),
@e1.rotate_entries(:counter_clockwise))
assert_equal(Matrix.empty(2,0),
@e1.rotate_entries(:half_turn))
assert_equal(Matrix.empty(0,3),
@e2.rotate_entries(:half_turn))
end

def test_rotate_with_numeric
assert_equal(Matrix[[4, 1], [5, 2], [6, 3]],
@m1.rotate_entries(1))
assert_equal(@m2.rotate_entries(:half_turn),
@m2.rotate_entries(2))
assert_equal(@m2.rotate_entries(:half_turn),
@m1.rotate_entries(2))
assert_equal(@m1.rotate_entries(:counter_clockwise),
@m1.rotate_entries(3))
assert_equal(@m1,
@m1.rotate_entries(4))
assert_equal(@m1,
@m1.rotate_entries(4))
assert_not_same(@m1,
@m1.rotate_entries(4))
assert_equal(@m1.rotate_entries(:clockwise),
@m1.rotate_entries(5))
assert_equal(Matrix.empty(0,2),
@e1.rotate_entries(1))
assert_equal(@e2,
@e2.rotate_entries(2))
assert_equal(@e2.rotate_entries(1),
@e2.rotate_entries(3))
assert_equal(@e2.rotate_entries(:counter_clockwise),
@e2.rotate_entries(-1))
assert_equal(@m1.rotate_entries(:counter_clockwise),
@m1.rotate_entries(-1))
assert_equal(Matrix[[6, 5, 4], [3, 2, 1]],
@m1.rotate_entries(-2))
assert_equal(@m1,
@m1.rotate_entries(-4))
assert_equal(@m1.rotate_entries(-1),
@m1.rotate_entries(-5))
end
end