Questions tagged [logic]

Questions related to mathematical logic and its use in computer science

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Factor-graph formula

We know that we can break a normal function $g$ in the following way: $$g(X_1, ..., X_n) = \Pi_if_i(S_i)$$ where $S_i \subseteq \{X_1, .. X_n\}$. Now let's look at $g$ as a graph with the vertex set $\...
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Which of these properties hold for all FO theories? (but not regarding fragments thereof)

Which of these properties hold for all FO theories? (but not regarding fragments thereof) a. Decidable b. At least expressive as propositional logic c. NP-complete a) Decidable: no, some first order ...
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SQL Error in my project

I have an issue with my project that I can not seem to solve. I have tested for errors and can not seem to solve it. Can someone point me in the right direction so that I can carry on with my project. ...
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Translating CTL into $\mu$-calculus

I have been studying $\mu$-calculus and right now I'm trying to translate CTL (computation tree logic) to $\mu$-calculus. I have found this article: https://www.win.tue.nl/~jfg/articles/CSR-10-09.pdf ....
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Create an Finite Deterministic Automata for a regular expression

I want to create a finite state machine that accepts the following language: $$ L=\{w\in\{a,b\}^* | w \text{ contains abb but not on the first position}\} $$ So I began by writing a regular expression ...
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Is Conjunctive Normal Form or not?

I have one formula that I do not understand why it is CNF and one that is not CNF, namely. p && !q (NOT NCF) and !!p(CNF). According to the exercise where I found these examples, 1 is not ...
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Is my UML Use Case Diagram valid?

I'm preparing an UML use case diagram for my following school project: ...
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Help me understand whether these critical pairs are joinable

I have the following TRS $R$: $$ l_1 = f(g(x)) \to f(x) = r_1 \\ l_2 = g(f(y)) \to g(y) = r_2 $$ I want to know if $R$ is confluent, and whether $g(f(f(x))) \leftrightarrow_R^* g(g(g(x)))$. I have ...
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Why is most research in logic and verification conducted in Europe rather than the US?

This is the CSRankings output for logic and formal verification for the last 10 years, worldwide: http://csrankings.org/#/index?log&world For the International Conference on Computer Aided ...
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How to combine multiple Boolean Functions in CDNF efficiently for implementation on a CPU?

I am trying to see how fast I can implement a 6-bits to 6-bites lookup table. Generally, I am attempting to do this by using the common method mentioned in CS textbooks of using the Quine-McCluskey ...
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Prove the boolean function E = F + G contains of the sum of the minterms of F and G

I'm given a boolean function E which is result of the sum of F and G (Where both F and G are boolean functions for sure). By using K-Map I can easily understand why E would have the sum of the ...
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is duality principle in boolean algebra is true for every expression

Let say A = 1 and B = 1 and then A+B = 1 now by using duality(replacing or gate by and gate and 1 by 0) we can say that, A.B = 0 but this is not 0, because 1.1 = 1, so please anyone clear my ...
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Automated algorithm design

There is a huge field of study dedicated to automated theorem proving. Is there any similar research dedicated to automated algorithm design? And is there any form of "duality" between these ...
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Check if given safety properties are regular, and if so construct NFAs

Let $\mathit{AP} = \{a, b, c\}$. Consider the following LT properties: Between two neighboring occurrences of $a$, $b$ always holds. Between two neighboring occurrences of $a$, $b$ occurs more often ...
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Name for a function on formulae that does not break the structure of given formula

I have two logics, $L_1$ and $L_2$, and a mapping $f: Formulas_{L1} \rightarrow Formulas_{L2}$, and want to argue that the mapping is "nice", in the sense that it is structure-preserving. ...
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Can every sentence of first-order logic be converted into an equisatisfiable equation in Boolean algebra?

There may be some theoretical literature, unknown to me, that addresses this question. If possible, I would like a practical approach to this problem. My attempt involves the use of an equational ...
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How expensive is it to verify that a gate is universal?

I know that a NAND gate is considered universal because we can use it to implement an AND, OR, and NOT gate. Given an arbitrary gate, or set of gates, how many operations would it take to verify if ...
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For a logic gate to be universal, must it necessarily be able to perform duplication?

It is said that a gate that can simulate AND and NOT is universal and able to recreate any classical circuit. I was looking at some of the circuits simulated by NAND, and for some of them, we need to ...
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first order logic to normal form order of operations

∃y∀x [A(x) ∧ B(y) -> C(x,y)] ∃y∀x [¬(A(x) ∧ B(y)) v C(x,y)] ∃y∀x [¬A(x) v ¬B(y) v C(x,y)] I need to convert the above to conjunctive normal form. I'm a ...
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39 views

Universal Quantifiers in QBFs

I've been looking into reductions to/from the TQBF language and have managed to get stuck on something that is almost certainly not true (or, if it is true I'm missing a significant computational cost ...
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33 views

Lambda calculus simplification excercise

Below is the lambda expression which I am finding difficult to reduce i.e. I am not able to understand how to go about this problem. (λx.λy.yx)z (λw.w) I am lost with this. if anyone could lead me in ...
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Two variants of Fredkin gate

Sometimes two outpus of Fredkin gate are swapped when constant bit is 0, sometimes when it is 1. What variant is right or more modern? If it was conscious decision to change behavior what was ...
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In theory, should neuromorphic computers be more efficient than traditional computers when performing logic?

There is this general sentiment about neuromorphic computers that they are simply "more efficient" than von Neuman. I've heard a lot of talk about neuromorphic computers in the context of ...
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Represent a DNF formula as a multivariate linear formula?

Lets say I have the following DNF: (x or y) and (z or i) / $(x\lor y)\land(z\lor i)$ How do I convert that into a polynomial form?
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Test two LTL expression trees for equivalence

Is there an algorithm on how to check if two LTL expressions (represented as binary trees) are semantically equivalent? Since there are many smaller equivalences such as $a\Rightarrow b \equiv \neg a \...
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Building an ALU on nandgame's website

I'm working on nandgame's website found here. I'm working on the ALU and here is an image of my implementation: My Implementation: And I compared it to this website's solution: Solution However when ...
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Can HOL be simulated in the CiC?

I was wondering if HOL (higher-order logic) can be simulated in the Calculus of Inductive constructions (CiC)
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What were the shortcomings of Robinson's resolution procedure?

Paulson et alii. From LCF to Isabelle/HOL say: Resolution for first-order logic, complete in principle but frequently disappointing in practice. I think complete means they can proof any true ...
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Is a or free SAT formula NP complete?

Let $L$ be the languague which contains all satisfiable formulas which do not have the or symbol $\lor $. Or more precise $$L=\{\phi | \phi \text{ is a satisfable formula which is only using the ...
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40 views

Is there a way to simplify redundant conditionals?

For example if I've this: if a == false then return true else if a == true and b == false return true else if a == true and b == true then return false can be ...
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134 views

How many clauses are required for SAT to be NP-hard in CNF formulas?

It is not hard to see that SAT for a CNF formula with $n$ variables and a constant number of clauses can be solved in polynomial time. On the other hand, it is not hard to see that a CNF formula with $...
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How are prime implicates of HORN-Formulas defined?

I'm confused about the definition of prime implicates in Horn formulas. For example in the paper of Kira 2012 on page 109 it is stated: Now in the paper of Boros 2010 on page 82 the following ...
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Equivalence of Horn formulas tractable?

Assume I have two Horn formulas $\phi_1, \phi_2$. Horn formulas are CNF formulas so that each clause has at most one unnegated literal. For example: $x_1 \wedge (\neg x_1 \vee \neg x_2 \vee x_3 )\...
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Equivalence of Krom formulas tractable?

Assume I have two Krom formulas $\psi_1, \psi_2$. Krom formulas are propositional formulas in CNF that have 2 literals in every clause. Each literal can be negated or unnegated. In other words, $\...
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Note down the possible states in a truth table

You are required to automate the control of the water tank in your home. There are two water contact sensors that turn to a TRUE state when in contact with water and a FALSE state when not. Sensor $1 (...
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Question on the “Tutorial implementation of dependently typed lambda calculus”

I have a slight technical struggle with this marvelous tutorial. On page 5 the tutorial talks about typing rules for Simply Typed Lambdas and presents following judgement as derivable via rules on ...
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Consistent theory based on L and not(A->A) is a theorem

I am working on this problem in which I have a theory $T$ based on language $\mathcal{L}$ and the only information we have is that T is consistent and $\vdash \lnot(A \rightarrow A)$. Given this ...
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Impredicativity example in HOL

From these notes pages 37-38. In HOL, I'm giving the task of proving: $\vdash \forall x^T. \forall y^T. (=_T x^T y^T) \implies (=_T y^T x^T)$ applying forall and implication introduction and the ...
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What is the best way to identify highly performing groups?

I am currently working on a project that involves sorting people into groups based on their ability to work well with others. While it is a bit of a simplification, I have a problem that is ...
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Circuits and formulas for Clique

Is it correct to say that the Clique Problem is in $P$ iff there exists a family of Boolean circuits $C$ to decide Clique whose sizes are bounded by a polynomial? And based on this question, does that ...
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What is the theoretical result of flattening a list containing only itself?

Consider the following python code X = [None] X[0] = X This has many fun properties such as X[0] == X and ...
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Understanding $\lambda \mu$-calculus in more programming way

I am learning $\lambda \mu$-calculus (self-study). I learned it because it seems very useful for understanding Curry-Howard correspondence (e.g understanding the connection between classical logic ...
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Situation calculus: how to find pre-conditions in 15-puzzle game?

I have been working on finding the preconditions for a situation calculus example for some time now. This example is called the game "15-puzzle" where you can find a discription here https://...
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Can we use Axiomitization to decide CTL*?

As the title says. There are axioms for CTL*, but can we use them to decide whether a formula is satisfiable? We can use the trick $p$ is satisfiable $\iff$ $\lnot p$ is not valid. My problem is that ...
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Substitution lemma for types

TAPL (page 549) proposes the following lemma in order to prove soundness of System F type system: Substitution lemma for types: $E, X, \Delta \vdash t: T \implies E, [X \mapsto S] \Delta \vdash [X \...
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Show that exist a finite set of clauses F in first-order logic that Res*(F) is infinite

I'm kind of desperate at this point about this question. A predicate-logic resolution derivation of a clause $C$ from a set of clauses $F$ is a sequence of clauses $C_1,\dots,C_m$, with $C_m = C$ ...
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37 views

Unification Algorithm without Occur Check

I have been reading about Unification algorithm here https://en.wikipedia.org/wiki/Unification_(computer_science)#A_unification_algorithm . And I wonder about the importance of occur check. I know ...
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32 views

Proving a certain primitive recursive function exists

Assume $f\colon ω × ω → ω$ is a computable function. How can we prove that there is a primitive recursive function $g\colon ω × ω → ω$ where the following holds: $∀n [∃s(f(n, s) = 1) ↔ ∃k(g(n, k) = 1)...
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Z-Specification = Routes

Im trying to make an invariant for this Z schema about routes. 1) The invariant should express that each route should contain at least 20 different places. First of all i thought of doing a universal ...

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