Questions tagged [predicate-logic]

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In predicate logic, is the “environment” only needed when free variables are present?

Suppose there exist no free variables in a given predicate logic formula. Is then a model alone sufficient to fully interpret the formula and make inferences? Don't we need an environment or variable ...
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1answer
18 views

Predicate Logic - negating the conclusion to prove logical consequence?

In Predicate Logic, if you want to prove the logical consequence using the method of resolution, do you ALWAYS start off by negating the conclusion?
1
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1answer
24 views

Predicate Logics - double negation HELP me understand

Sorry for maybe a silly question but i need to understand how ¬(¬∀x ¬A(x)) equals ∀x ¬A(x) In my mind, the negation before the parenthesis will be applied to both ¬∀x and ¬A(x). So it would look like ...
2
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1answer
29 views

Computability: Proving a predicate is not recursively enumerable

Let P(p) <=> for each x, comp(p,x) is defined. Can anyone explain to me how to prove that P is not RE (recursively enumerable) ?
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0answers
18 views

Natural deduction proof without any predicate

I am gaving trouble proving a natural deduction proof when there is no predicate given. Only conclusion is given. I understand the rules of elimnations, inclusions, IPs and others but I having trouble ...
0
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1answer
52 views

Hoare triple: Loop invariant and correctness

The following Hoare triple in which variable a is an array of integers, and len, max, i, n, j and m are integer-valued variables. Provide a loop invariant (using predicate logic) suitable for proving ...
2
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0answers
58 views

Hoare triple: Loop invariant and partial correctness

Below there is Hoare triple in which variable $a$ is an array of integers, $len$, $x, i$ are integer-valued variables, and $r$ is a Boolean-valued variable. I have to provide a loop invariant (using ...
2
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1answer
103 views

Negation of the semantics of the Until operator in LTL

I have been looking at the Until operator and the release operator and when introduced to the release operator it was suggested that it is equivalent to: $\phi R \psi \equiv \neg(\neg\phi U \neg \psi)...
1
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2answers
69 views

Must $x$ and $y$ be different in a statement of the form $\forall x \forall y \cdots$?

Given the following predicate formula $F$: $$\forall x \forall y [(\text{italian}(x) \Rightarrow (\text{winWC}(y) \Rightarrow \text{happy}(x))]$$ I am having trouble understanding whether $x$ and $y$...
0
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1answer
24 views

What does it mean to logically imply another predicate?

Consider the following predicate formulas. $F1: \forall x \exists y ( P(x) \to Q(y) ).$ $F2: \exists x \forall y ( P(x) \to Q(y) ).$ $F3: \forall x P(x) \to \exists y Q(y).$ $F4: \exists x P(x) \...
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1answer
38 views

predicate logic proof of 2 numbers

For any two different numbers there is an number in between. I'm trying to write this in predicate logic and have no idea how to do it, since I need 2 variables X and Y? For all x there exists a y ...
-1
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1answer
46 views

predicate logic/binary relation help

(1) ∀x, y, z (x < y ∧ y < z → x < z) (transitivity) (2) ∀x ¬(x < x) (antisymmetry) (3) ∀x, y (x < y ∨ x = y ∨ y < x) (linearity) I need to give an example of a (nonempty) ...
1
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1answer
58 views

Discrete Mathematics Proofs for ∃ and ∀

Premises or Givens: $∃x(A(x) → B(x))$ $∀x (B(x) → K(x))$ To Prove: $∃x(A(x) → K(x))$ My Solution: $A(z) → B(z)$ From premise and Existential instantiation $x$ for $z$ $B(z) → K(z)$ From ...