From: merch-redmine@... Date: 2019-08-23T22:35:50+00:00 Subject: [ruby-core:94513] [Ruby master Bug#12356] Vector covector incorrect multiplication with another vector. Issue #12356 has been updated by jeremyevans0 (Jeremy Evans). Assignee set to marcandre (Marc-Andre Lafortune) Status changed from Open to Assigned I don't think this is a bug, but I'll let marcandre make the determination. `Vector` can't be multipled with `Vector`, you get an error. You can multiple a `Vector` by a `Matrix` and vice-versa by design, and `Vector#covector` returns a `Matrix`. You can multiple a `Matrix` by a `Matrix` only if the column_count of the receiver is the row count of the argument. Whether `Vector` is good design or bad design I'm not going to speculate on. However, you could consider using NMatrix (https://rubygems.org/gems/nmatrix), as that represents vectors as matrices. ---------------------------------------- Bug #12356: Vector covector incorrect multiplication with another vector. https://bugs.ruby-lang.org/issues/12356#change-80949 * Author: edmorte (Rafael Silva) * Status: Assigned * Priority: Normal * Assignee: marcandre (Marc-Andre Lafortune) * Target version: * ruby -v: ruby 2.2.4p230 (2015-12-16 revision 53155) [x86_64-linux] * Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN ---------------------------------------- Version 2.2.4 v1 = Vector[2,3,4] v2 = Vector[4,5,6] v1.covector.row_size #1 v1.covector.column_size #3 v2.covector.row_size #1 v2.covector.column_size #3 Vector does not have distinction between row and column, there's no column vector notion in the language. v1 * v2.covector #Matrix[[8,10,12],[12,15,18],[16,20,24]] # Should be illegal. But works like if v2.covector is transposed / column vector which it's clearly not. v1.covector * v2.covector #ExceptionForMatrix::ErrDimensionMismatch: Matrix dimension mismatch # Expected v1 * v2 #ExceptionForMatrix::ErrOperationNotDefined: Operation(*) can't be defined: Vector op Vector # No comments, see my observation below. v1.covector * v2 #Vector[47] #Again covector treated like transposed / column vector. Personal observation: Terrible choice to represent Vector like an Array, Vector should be a shortcut to Matrix. -- https://bugs.ruby-lang.org/ Unsubscribe: