invariants Questions

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How would you go about proving the correctness of merge sort with reasoning over the states of loop invariants?.The only thing that i can visualize is that during the merge step the subarrays(invar...
Pygmy asked 9/11, 2016 at 3:23

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I've been looking at various Node.js projects' source, and I've noticed that some people use invariant. From what I understood, invariant is a tool that lets you put assertions in your code, and ra...
Delora asked 20/8, 2016 at 14:22

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I understand from the Go tour that upper case variables are meant to be exported, while lower case variables in a struct are not exported. But I am trying to achieve something else. In Java, I coul...
Equal asked 13/10, 2021 at 12:30

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Using a std::shared_ptr expresses shared ownership and optionality (with its possibility to be null). I find myself in situations where I want to express shared ownership only in my code, and no o...
Tyrosine asked 31/1, 2017 at 10:30

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I am trying to prove that my implementation of Select Sort in Ada is correct. I have tried a few loop invariants, but using gnatprove only proves inner loop's invariant: package body Selection with...
Hamnet asked 30/3, 2021 at 12:8

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I aim to prove that the Horner's Rule is correct. To do so, I compare the value currently calculated by Horner with the value of "real" polynominal. So I made this piece of code: package ...
Uriel asked 24/3, 2021 at 18:7

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The word seems to get used in a number of contexts. The best I can figure is that they mean a variable that can't change. Isn't that what constants/finals (darn you Java!) are for?
Limner asked 21/9, 2008 at 20:42

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I often see the term Invariants in DDD. Here Dino Esposito talks about it. If I look at the .NET library, I see a ValidationAttribute class. Are Invariants and validation rules the same? For exampl...
Unthread asked 12/5, 2015 at 12:2

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Class invariants definitely can be useful in coding, as they can give instant feedback when clear programming error has been detected and also they improve code readability as being explicit about ...
Seriocomic asked 16/11, 2016 at 19:48

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As seen on Introduction to Algorithms (http://mitpress.mit.edu/algorithms), the exercise states the following: Input: Array A[1..n] and a value v Output: Index i, where A[i] = v or NIL if v does ...
Burra asked 7/4, 2011 at 17:20

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Can I write a type guard asserting something about one or multiple sub-objects of an argument? In pseudo-code, it might look like this: class C { a: number?; b: string?; function assertInitial...
Homeopathist asked 6/4, 2018 at 2:52

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I have encountered a problem while using Invariants with Code Contracts. I want to define an Invariant within my abstract class but it is simply ignored. The code below shows my interface and the ...
Collencollenchyma asked 18/3, 2015 at 13:41

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I am looking for advice on where to add validation rules for domain entities, and best practices for implementation. I did search and did not find what i was looking for, or i missed it. I would l...

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Is there a way for me to only export specific getters xor setters from a module with a lens? For example, let's assume a data structure that has an invariant of being always >= 0, being modifi...
Cyprinid asked 14/12, 2014 at 23:9

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I am trying to understand these two concepts. The manual I am reading is very brief on them and things like multipass algorithm are new to me. I would like to have some examples (not code) of where...
Terrigenous asked 28/4, 2014 at 15:30

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I googled the topic, but besides Wikipedia I didn't find any further useful documentation or articles. Can anybody explain to me in simple words what it means or refer me to some nice and easy to...
Extraversion asked 17/1, 2012 at 22:0

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I'm having my first attempt at DDD and I'm running into a problem with aggregate design. My application contains 3 Entities; Graph, Node, Link. Each of these entities has a name property which can...
Mombasa asked 31/7, 2013 at 10:27

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Context (Edit) Some clarification was on demand, so I'll try to sum up what influences the question. The goal of the project is to provide a certain functionality to programmers, most probably i...
Donovan asked 11/4, 2013 at 21:21

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In DDD can an aggregates invariant include a rule based on information in a another aggregate? Now I don't think so, however this causes me a problem and I don't know how to solve it. I have an en...
Concave asked 5/4, 2013 at 13:46

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For OOP, are immutable and invariant synonymous? I have a vague feeling that a difference exists, but I'm not sure. I believe that immutable typically is applied to objects, while invariant is t...
Longerich asked 5/10, 2012 at 15:48

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I've been trying to wrap my head around how move semantics in C++11 are supposed to work, and I'm having a good deal of trouble understanding what conditions a moved-from object needs to satisfy. L...
Holzman asked 23/8, 2012 at 15:23

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I'm moving my first steps in Scala and I would like to make the following code works: trait Gene[+T] { val gene: Array[T] } The error that the compiler gives is: covariant type T occurs in inva...
Coyote asked 30/7, 2012 at 12:48

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I am reading the book Java Concurrency in Practice and getting a little bit confused with these terms: Pre condition Post condition Invariants Can someone please explain me them (with an exampl...
Apocarpous asked 4/7, 2012 at 15:30

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Long story short, I would like to be able to store generics using different type parameters in an array, by using a parent type to all the types used. MSDN mentioned it was impossible, as generics ...
Diagraph asked 22/6, 2012 at 17:52

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I want to define a type so that all construction goes through module members that can preserve invariants, but allow destructuring for pattern matching. I'm just learning OCaml but the following a...
Ricard asked 22/5, 2012 at 20:50

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