Supplementary Errata for Huth & Ryan (3rd Printing)

p.2, declarative sentence (3)

this version of Goldbach's conjecture is trivially false: 2 is an even natural number, but cannot be written as the sum of two primes!

p.2, declarative sentence (4)

under the very reasonable assumption that there are no Martians, this claim is vacuously true!

p.5,l.1

Actually, there exists technology (aka parsers) such that computers can disambiguate even in the absence of brackets!

p.35, Definition of a^b

it is not clear which properties of the real numbers we assume.

p.97, Exercise 2.1 #2

f and g have the wrong arity in the example f(x,g(y,z),z).

p.106,l.3

The sentence "x serves as an argument to a predicate..." is a bit unclear. The point is that 'x' is used as a term, and therefore should be replaced by a term.

p.124, the reverse argument

According to the requirements on p.14, the use of /\i in the last line is not permissible. Instead, we should prove \psi outside the box, as is easy to do.

p.139, Exercises 2.7 #4(a)

"If psi is a semantically entailed..." should be "If psi is semantically entailed..."

p.141, l.-5

the proof rule used is actually not 'RAA', but "only" 'not introduction' (with 'not elimination' as intermediate step)

p.179, definition of SAT, case for phi1 -> phi2

on the right hand side, "phi" should be "phi1"

p.228, l.13

"If our calculus is any good, the notions |-par and |= par should coincide". Well, at least we should have soundness, but a calculus which is not complete might still be very useful!

p.253. l.5

"For example...". The example does no longer (after the error in the first printing was fixed) illustrate that minimal-sum sections are not necessarily unique!

• Torben Amtoft