5 ms·

If a+b != b+a that breaks the commutativity property of addition.

• jcheng 8y ago
  "a"+"b" != "b"+"a" already.
• davidwtbuxton 8y ago
  Yes, but I still want this for combining dictionaries. Python already violates this property, I don't find it confusing. Python 3.7.2 (default, Dec 30 2018, 08:55:50) [Clang 10.0.0 (clang-1000.11.45.5)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> 'foo' + 'bar' == 'bar' + 'foo' False >>> ['foo'] + ['bar'] == ['bar'] + ['foo'] False
• frabert 8y ago
  Commutatitivity does not need to always hold. Multiplication is not commutative on matrices, but we still use it often and write it as a product nonetheless
  • whatshisface 8y ago
    Python actually supports a special operator @ for non-commutative matrix products.
  • Koshkin 8y ago
    In mathematics, the ‘multiplication’ operation is not assumed to be commutative, whereas the ‘addition’ operator is used specifically to indicate commutativity. So, for example, using the plus sign for string concatenation goes against this tradition.
• phkahler 8y ago
  That property is not universal, and it is currently being defined for Python dictionaries. You can't break a property that isn't defined yet. ;-)
  • selimthegrim 8y ago
    Is this what changed in 3.5?
• dnautics 8y ago
  To be fair, IEEE fp addition is noncommutative in corner cases.