From: Run Paint Run Run <redmine@...>
Date: 2009-05-26T09:54:33+09:00
Subject: [ruby-core:23559] [Bug #1517] Matrix[] Performs No Argument Validation, Confusing Some of Its Instance Methods

Bug #1517: Matrix[] Performs No Argument Validation, Confusing Some of Its Instance Methods
http://redmine.ruby-lang.org/issues/show/1517

Author: Run Paint Run Run
Status: Open, Priority: Normal
ruby -v: ruby 1.9.0 (2008-06-20 revision 17482) [i486-linux]

The Matrix[] constructor accepts anything as argument. This can cause problems for its instance methods. For example, consider a Fixnum:

    >> m = Matrix[1]
    => Matrix[1]

This works as you'd expect. But then:

    >> m.row(0)
    TypeError: can't dup Fixnum
	from /usr/lib/ruby/1.9.0/matrix.rb:1132:in `dup'
	from /usr/lib/ruby/1.9.0/matrix.rb:1132:in `init_elements'
	from /usr/lib/ruby/1.9.0/matrix.rb:1124:in `initialize'
	from /usr/lib/ruby/1.9.0/matrix.rb:1117:in `new'
	from /usr/lib/ruby/1.9.0/matrix.rb:1117:in `elements'
	from /usr/lib/ruby/1.9.0/matrix.rb:303:in `row'
	from (irb):20
	from /usr/bin/irb1.9:12:in `<main>'

Or:

    >> m.column_size
    => 4

Which leads to:

    >> m.column_vectors
    => [Vector[1], Vector[0], Vector[0], Vector[0]]

If such arguments are accepted, Matrix should coerce them into a matrix. Presumably, the easiest approach would be to have Matrix[1] == Matrix[[1]]. Otherwise, Matrix[] should raise an ArgumentError if it doesn't receive an Array. Ideally, you should only be able to create matrices of Arrays of Numeric-like objects. The current behaviour is non-intuitive, and invites bugs.


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