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    Home Unlabelled « Words in a Day » This project was made for a four-days workshop on data visualization in relation to the idea of "quantified self" (See link in Comment for more) IUAV University of Venice Computer Science

    « Words in a Day » This project was made for a four-days workshop on data visualization in relation to the idea of "quantified self" (See link in Comment for more) IUAV University of Venice Computer Science

    May 04, 2021

    « Words in a Day » This project was made for a four-days workshop on data visualization in relation to the idea of "quantified self" (See link in Comment for more) IUAV University of Venice Computer Science

    « Words in a Day » This project was made for a four-days workshop on data visualization in relation to the idea of "quantified self" (See link in Comment for more) IUAV University of Venice

    Posted: 03 May 2021 11:42 AM PDT

    New Highspeed Control Strategy For Energy-Efficient Data Storage of The Future

    Posted: 04 May 2021 02:40 AM PDT

    [Discussion] A class should have state or dependencies, but not both

    Posted: 04 May 2021 12:38 AM PDT

    This principle "feels" right, but I'm working through trying to formulate it properly.

    Consider a point class (in pseudo-code because lazy):

    class Point private x, y construct(x, y) draw(Drawable surface)

    (Instead of surface, it could also be a save-function with a database connection as argument (or indeed any type of persistence)).

    If the surface was instead injected into the constructor, the point would look like:

    class Point private x, y, surface constructor(x, y, surface)

    Isn't that weird, to have two properties related to state, and then a third property related to something completely different? Especially when it's something effectful, like drawing or writing to disk.

    On the other hand, you can imagine a command object class like this:

    class InstallApp private db, io, logger, mailer constructor(db, io, logger, mailer) execute(app)

    In this case, all dependencies are effectful classes. Makes more sense, right? And then the app class has only "pure" properties, like User or Configuration.

    A rectangle depending on points is also OK, since the points are pure:

    class Rectangle private bottomLeft, topRight constructor(Point bottomLeft, Point topRight) // draw, save, etc

    Another way to phrase it is that classes should only depend on other classes in the same layer (domain layer vs "effectful" layer).

    The major drawback is that no language can actually distinguish between a dependency and "normal" class property. Possibly they should have different semantics? Or the possibility to separate pure and effectful classes.

    Thoughts?

    submitted by /u/usernameqwerty005
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    Online Computer Network Certification Exam

    Posted: 03 May 2021 10:42 PM PDT

    Is Hoare logic a logic system or a theory in some logic system?

    Posted: 03 May 2021 04:10 PM PDT

    (1) p872 of http://www.worldcolleges.info/sites/default/files/aaby.pdf says

    The axiomatic semantics of a programming language define a mathematical theory of programs written in the language.

    In the first logic system, a theory is a set of sentences closed under |- or |=.

    Is Hoare logic a theory in some logic system (such as propositional logic, first order logic)? If yes, which logic system?

    Or is Hoare logic a logic system itself?

    (2) If Hoare logic is a logic system itself, https://en.wikipedia.org/wiki/Hoare_logic says

    Hoare logic (also known as Floyd–Hoare logic or Hoare rules) is a formal system with a set of logical rules for reasoning rigorously about the correctness of computer programs.

    while https://en.wikipedia.org/wiki/First-order_logic says

    First-order logic is a collection of formal systems used in mathematics, philosophy, linguistics, and computer science.

    In the first order logic system, nonlogical symbol sets are up to choice, and for different nonlogical symbol sets, there are different formal first order languages.

    In Hoare Logic, is it only one formal system and only one formal language? Or is it like the first order logic system, where there are multiple formal systems (i.e. multiple formal languages)?

    Does Hoare logic only have one proof system, while FOL can have multiple equivalent proof systems (e.g. Sequent calculus, Hilbert system)?

    Does Hoare logic have semantics, as FOL has semantics?

    Thanks.

    submitted by /u/timlee126
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    New Proof Reveals That Graphs With No Pentagons Are Fundamentally Different

    Posted: 26 Apr 2021 10:22 AM PDT

    Can every amortized algorithm be de-amortized?

    Posted: 26 Apr 2021 04:37 PM PDT

    I recently learned about Fibonacci heaps for the first time. This data structure offers (i) enqueue, (ii) merge, (iii) decrease-key, (iv) delete, and (v) extract-min, all in amortized constant time, except for extract-min, which is in amortized logarithmic time.

    Additionally, there's apparently an even "fancier" data structure called strict Fibonacci heaps. This data-structure supports all the same operations in all the same times, except they're amazingly worst-case rather than amortized.

    This gives rise to a general question. Can all amortized algorithms be de-amortized? Or can only some of them, and if so, are there general properties that allow de-amortization? In the back of my head, I have in mind the result of Avi Wigderson (which I also just learned about) that an important class of randomized algorithms can in theory be de-randomized (made deterministic) with the same time-complexity. I wonder if something similar could be at work here.

    submitted by /u/haroldgparker
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