# Petr Pudlák

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bio website petr.pudlak.name location Czech Republic age member for 1 year, 7 months seen Feb 22 at 19:03 profile views 125

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 Jan8 comment Automatic theorem prover for proving simple theorems? Are you interested in propositional logic or first-order logic? Sep14 comment How to express paritioning of a set into two exact halfs using combinatorial species? @ZhenLin I'd like to express it using the basic operations (which are described in the Wikipedia article). Sep14 revised How to express paritioning of a set into two exact halfs using combinatorial species? added 24 characters in body Sep14 revised How to express paritioning of a set into two exact halfs using combinatorial species? added 55 characters in body Sep14 asked How to express paritioning of a set into two exact halfs using combinatorial species? Aug8 awarded Yearling Jun29 comment Intuition of implication in propositional logic Another analogy is: If you don't eat your vegetables, you don't get your desert. If you don't eat the vegetables, I keep the promise and I won't give you the desert. If you do eat them, I don't have to do anything (because the premise is false). Neither way I'm obliged to give you the desert. Jun29 comment Prove p from ¬¬p No problem, I added it to my answer. Jun29 revised Prove p from ¬¬p Added a proof of $\phi\Rightarrow\phi$. Jun15 comment Prove p from ¬¬p That's much better. It's correct now, except for step 4). In this logic system, you have no notion of $\lor$, and if you had, you have to prove its relation to $\Rightarrow$ as well as that $p\lor\lnot p$ is a tautology. Hint: You can prove $\phi\Rightarrow\phi$ by taking a suitable instance of ID and then using using MP twice, each time using a (different) suitable instance of II. Jun10 comment Prove p from ¬¬p You've made several mistakes. The most important is in 2-3 where you eliminate the double negation. This is what you're trying to prove! So you've created a circular proof. Less important: It's true that $a \Rightarrow a$ is valid, but you have to prove it. Also you use the rule $b,\, a \Rightarrow (b\Rightarrow c)\,\vdash\, a\Rightarrow c$, which you need to prove first. Also, to derive 5 you don't need 4 (it's an axiom). Derivation of 7 from 6 doesn't make any sense to me. Jun9 answered Prove p from ¬¬p Jun9 awarded Citizen Patrol Jun8 comment Is there an algorithm to separate lambda calculus terms using Böhm's theorem? Oh, I didn't understand that you meant the combinators - the convention is that lower case letters are reserved for variables. Jun8 comment Is there an algorithm to separate lambda calculus terms using Böhm's theorem? This has been answered recently on CS. Note that you can't separate $i$ and $k$, because they have free variables. Böhm's theorem applies only for closed terms. Jun1 accepted What is the distribution of primes modulo $n$? May27 comment What is the distribution of primes modulo $n$? Isn't it the other way round - more primes for a non-residue than for a residue? May27 comment What is the distribution of primes modulo $n$? Nice, Chebysev's bias explain exactly why I observed more primes $\equiv 2 \mod 3$ than $\equiv 1$. May27 asked What is the distribution of primes modulo $n$? May23 accepted How uniform is the distribution of $n+sm$ for an irrational $s$?