# Tagged Questions

34 views

### Trying to disprove a statement - some partial working included

I am trying to find a counter example to show that the statement below is false, but I am having difficulty in trying to find a reasonable argument. Here is the statement: $n^2-12n + 35 \geq 0$ for ...
35 views

### The approximation rule implies the equality rule in systems of type assignments

I'm reading Barendregt's Lambda calculi with types (1992). In Proposition 4.1.4.1., he "proves" a lemma which shows the approximation rule implies the equality rule in typed lambda-calculi à la ...
703 views

### Why can't reachability be expressed in first order logic?

I'm wondering why we can't express graph reachability in first order logic in pretty much exactly the same way we express it in second order existential logic. For SOL, one definition is : 1 . L is ...
161 views

### What is this proof syntax (Hoare 1974)?

I'm reading the seminal "Monitors" paper by Hoare. On page 4 he proceeds with a logical proof using syntax I've never seen before, and neither know what it's called or how to properly read it. ...
1k views

### How can I learn about proofs for computer science?

I study computer science at a university. My school offers several courses where various proofs are expected, but there is no course that introduces the fundamental concepts of proofs and how to write ...