Module: Vector2d::MatrixInterop

Included in:
Vector2d
Defined in:
lib/vector2d/matrix_interop.rb

Overview

Interoperability with the Matrix and Vector classes from the standard library.

The matrix library is a bundled gem, and is only loaded when a conversion needs it. Nothing here loads it on its own, so it has to be in the Gemfile of applications using these methods.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.matrix?(object) ⇒ Boolean

Is the object a Matrix?

Parameters:

  • object (Object) —

    any object

Returns:

  • (Boolean) 


16
17
18
 
# File 'lib/vector2d/matrix_interop.rb', line 16

def matrix?(object)
  defined?(::Matrix) && object.is_a?(::Matrix)
end

.vector?(object) ⇒ Boolean

Is the object a Vector?

Parameters:

  • object (Object) —

    any object

Returns:

  • (Boolean) 


24
25
26
 
# File 'lib/vector2d/matrix_interop.rb', line 24

def vector?(object)
  defined?(::Vector) && object.is_a?(::Vector)
end

Instance Method Details

#coerce(other) ⇒ Array(::Matrix, ::Vector), Array(self, self)

Implements Ruby's coercion protocol for matrices, so a vector can be the right hand operand of a matrix. The result is a Vector, as the matrix is the receiver of the operation.

Matrix[[0, -1], [1, 0]] * Vector2d(3, 4) # => Vector[-4, 3]

Use #transform to get a Vector2d back.

Vectors are coerced the other way around, as the two dimensional vector is the more specific type.

Vector[1, 2] + Vector2d(3, 4) # => Vector2d(4,6)

Parameters:

  • other (Vector2d, Array, String, Hash, Integer, Float, Rational, BigDecimal, ::Vector, ::Matrix) —

    anything Vector2d.parse accepts

Returns:

  • (Array(::Matrix, ::Vector), Array(self, self)) —

    the other operand and this vector, converted to a Vector when the other operand is a Matrix



46
47
48
49
50
 
# File 'lib/vector2d/matrix_interop.rb', line 46

def coerce(other)
  return [other, to_vector] if MatrixInterop.matrix?(other)

  super
end

#to_matrix ⇒ ::Matrix

Converts vector to a 2x1 column Matrix from the standard library, the same shape Vector#to_matrix returns.

Vector2d(2, 3).to_matrix # => Matrix[[2], [3]]

Returns:

  • (::Matrix) —

    a 2x1 column matrix



58
59
60
61
 
# File 'lib/vector2d/matrix_interop.rb', line 58

def to_matrix
  require "matrix"
  ::Matrix[[x], [y]]
end

#to_vector ⇒ ::Vector

Converts vector to a Vector from the standard library. This is the only to_* method that leaves the class behind, #to_f_vector and #to_i_vector return a vector of this class.

Vector2d(2, 3).to_vector # => Vector[2, 3]

Returns:

  • (::Vector) 


70
71
72
73
 
# File 'lib/vector2d/matrix_interop.rb', line 70

def to_vector
  require "matrix"
  ::Vector[x, y]
end

#transform(matrix) ⇒ self

Multiplies a 2x2 Matrix by this vector, treating the vector as a column. Unlike coercion, this keeps the class of the receiver.

Vector2d(3, 4).transform(Matrix[[0, -1], [1, 0]])
# => Vector2d(-4,3)

Raises TypeError unless the argument is a Matrix, and ErrDimensionMismatch unless it has two columns.

Parameters:

  • matrix (::Matrix) —

    a matrix with two columns

Returns:

  • (self)

Raises:

  • (TypeError) 


86
87
88
89
90
91
 
# File 'lib/vector2d/matrix_interop.rb', line 86

def transform(matrix)
  raise TypeError, "#{matrix.class} is not a Matrix" unless MatrixInterop.matrix?(matrix)

  result = matrix * to_vector
  build(result[0], result[1])
end