Issue #10855 has been updated by Marc-Andre Lafortune.

Assignee set to Marc-Andre Lafortune

Interesting.

I'm thinking it might be best to do the conversion even if some entries are not integral. Why do you feel it's best to have uniform types accross a matrix, in particular when would having an Integer instead of a Rational be a problem?

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Bug #10855: [PATCH] Matrix#inverse returns matrix of integers whenever possible
https://bugs.ruby-lang.org/issues/10855#change-51506

* Author: Lito Nicolai
* Status: Open
* Priority: Normal
* Assignee: Marc-Andre Lafortune
* ruby -v: 2.3.0
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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Currently, Matrix#inverse returns a matrix of Rationals, even when each
element has a denominator of 1. This leads to 

	> x = Matrix.identity 3
	=> Matrix[[1, 0, 0],
                  [0, 1, 0],
                  [0, 0, 1]]

	> x.inverse
	=> Matrix[[(1/1), (0/1), (0/1)],
		  [(0/1), (1/1), (0/1)],
                  [(0/1), (0/1), (1/1)]]

Even though `Matrix.identity.inverse` should be identical to `Matrix.identity`.

This patch guarantees that Matrix#inverse will return a matrix of integers
whenever it can. To maintain uniform types across a matrix, the conversion 
is only performedif *every* element can be converted to an integer.

---Files--------------------------------
matrix_inverse_to_integer.patch (2.14 KB)


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