On Mon, 18 Nov 2013 19:33:01 -0800, Rick Johnson wrote: > I've never *really* been crazy about the plus operator concatenating > strings anyhow, however, the semantics of "+" seem to navigate the > "perilous waters of intuition" far better than "*". > > Addition of numeric types is well defined in maths: Take N inputs > values and *reduce* them into a single value that represents the > mathematical summation of all inputs.
Which sum would that be? Addition of vectors, matrices, quaternions, tensors, something else? Do you perhaps mean the Whitney Sum? http://mathworld.wolfram.com/WhitneySum.html Ah, no, you're talking about addition of Real numbered values, where nothing can *possibly* go wrong: py> 0.1 + 0.1 + 0.1 == 0.3 False Hmmm. Oh well, at least we know that adding 1 to a number is guaranteed to make it bigger: py> 1e16 + 1 > 1e16 False Surely though, the order you do the addition doesn't matter: py> 1.5 + (1.3 + 1.9) == (1.5 + 1.3) + 1.9 False Dammit maths, why do you hate us so??? So, explain to me again, what is the *precise* connection between the mathematical definition of addition, as we learn about in school, and what computers do? > HOWEVER, > > Addition of strings (concatenation) requires interpreting the > statement as a more simplistic "joining" process of : take N inputs > and join them together in a *linear fashion* until they become a > single value. Ah, you mean like addition in base-1, otherwise known as the unary number system, also known as a tally. So if you want to add (decimal) 3 and 5 using base-1, we would write: ||| + ||||| and concatenating the tallies together gives: |||||||| which if I'm not mistaken makes 8 in decimal. > There is an inconsistency when applying the "*" operator between > numerics and strings. In the case of numerics the rules are widely > understood and quite logical, HOWEVER, in the case of "string products", > not only are rules missing, any attempt to create a rule is illogical, > AND, we've broken the consistency of the "*" interface! A foolish consistency is the hobgoblin of little minds. Just because you can't define a sensible meaning for str * str doesn't mean you can't define a sensible meaning for str * int. > py> "a" * "4" > 'aaaa' > > Okay, that makes sense, but what about: > > py> "a" * "aaaa" > > That will haunt your nightmares! You're easily terrified if you have nightmares about that. I can't imagine what you would do if faced with the M-combinator applied to itself. > But even the previous example, whilst quite logical, is violating the > "contract of transformations" What contract of transformations? -- Steven -- https://mail.python.org/mailman/listinfo/python-list
