Rob Stewart wrote:
From: FlSt@gmx.de
Rob Stewart wrote:
[...] namespace: boost::multivalues base class: multivalue all_of: all_values any_of: any_value none_of: no_values one_of: one_value
Sounds a bit like a container type for me. It's nothing more than a functional extension for ranges (or container), some kind of algorithm. I don't know!
It does sound a little like a container type, but what container would be named like those? That is, I don't think they would make good container names, so I think they fit our purposes reasonably well.
I aggree that they wouldn't make good container names (multivalues could be another name for array). And I think multivalues are a better name than junctions, because the concept we are discussing differs a lot from the perl idea, what is a good reason for an other name. The name "junctions" distinguishes the relation between the values, which would fit better to my interpretation I described in my previous posting. So I will aggree with "multivalues" until someone has a better idea.
[...]
I understand xxx_of as giving a logical linkage to the values of a list and I think this is what Perl also does: all_of = and, any_of = or, one_of = xor and none_of = not any_of. Do you agree?
I'm not certain I can agree. I understand that using that definition does simplify the implementation, but "all" doesn't quite evoke "and," nor "any" "or," nor "none" "not." "one" does reasonably evoke "xor," however.
My interpretation (and i think also perl does so) is based on the boolean algebra where the operators "All of" (the A on it's head) and "Exists" (the mirrored E) are used in analogy to the sum and product operators in numeric algebra. So i think the names have sense. Your interpretation has is a higher-level approach. The longer I think about this, the more I belife there are justifications for both interpretations. What do you think? BTW: Today I tried to install the Perl 6 interpreter Pugs, but I didn't get it to work. I wanted to analyze the Perl 6 implementation of junctions especially the behaivor of comparisons, because I don't want to tell something wrong here. The only experiences I have are with the Quantum::Superpositions module which behaves like my implementation, except that my current implementation doesn't return a new junction and doesn't support algebraic operations.
I didn't pay enough attention to the details of the Perl approach, so I didn't get mired in them. That left me to interpret "all," "and," "none," and "or" at face value. That also left me to find some strange combinations that were confusing. (More below.)
That is want I meant above. I really don't think that your approach is wrong or bad, but I must rethink completely to follow your thoughts.
false <---- different result! This is the proove that in my interpretation not all equality comparisons are symetric
I think allowing asymmetry in these expressions will cause great confusion. This is especially true when it isn't required.
From your viewport of multivalues I aggree and understand what you mean.
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I think it would be more sensible when read, and remains easy enough to explain if we provide symmetry and these definitions:
all_of: every value must satisfy the test with the same other value any_of: at least one value must satisfy the test each_of: every value must satisfy the test n_of: exactly n values must satisfy the test none_of: no value may satisfy the test one_of: exactly one value must satisfy the test
I must admit that I can't say something useful about this now, I need some more time to think about it, because I'm still affected by the Perl implementation.
I invented n_of (n_values) when I was considering none_of and one_of and I thought to generalize it.
You can generalize it a step further when you can give a range to n_m_of(): n minimum number of values that must satisfy the test and m maximum number of values that must satisfy the test. Ok, ok no more complexity as necessary ;-) Your n_of would also be useful with the junctions approach (This provides all steps between "and" and "or" inclusive "xor" in one function).
[..]
For the one_of(x) == one_of(y) example, I think it is reasonable to think of it as finding exactly one value from x and exactly one from y that satisfies x[n] == y[m]. That's how it reads. (I haven't even attempted to see whether that's how your interpretation would answer.)
In my interpretation this would be equivalent to: ( x[1] == y[1] ^^ x[1] == y[2] ^^ ... ^^ x[1] == y[m] ) ^^ ( x[2] == y[1] ^^ x[2] == y[2] ^^ ... ^^ x[2] == y[m] ) ^^ ... ( x[n] == y[1] ^^ x[n] == y[2] ^^ ... ^^ x[n] == y[m] ) What means this expression is true when x has exactly one value which is equal to exactly one value of y.
I have to review my design to make sure I'm doing everything correctly, and I have a couple of tests that fail still. Once I finish, I'll upload it for your inspection.
I'm very courious about it. Sincerly Florian