Lectures onType Theory
ch:soft-linear-logic: ch:soft-linear-logic
appendix sectionsolutions

ch:soft-linear-logic: ch:soft-linear-logic

exercise 56.1.

Use two identities AA, combine their disjoint contexts with tensor introduction to obtain A,AAA, and apply rank-2 multiplexing to conclude !AAA. For the additive formula, apply rank-1 multiplexing separately to two copies of the identity derivation, obtaining two derivations of !AA; additive conjunction introduction reuses that same context and concludes !AA&A. Rank 0 exposes no copy and therefore acts as weakening.

exercise 56.2.

First Wu&v=X+2+3+1=X+6. Boxing gives W!(u&v)=X2+6X+1, which evaluates to 17 at rank 2. Its degree is one more than the larger degree of u and v.

exercise 56.3.

At rank 2, the family has bounds km2m. Since the exponent m grows with the encoded net, no fixed-degree polynomial covers the family by the corollary. The changed hypothesis is that u, and hence its degree, was fixed.

exercise 56.4.

The degrees are 2 and 3, so the representation sequent is S(6)B: it has six string assumptions. Coefficients change how many fixed transition components are composed; the number of antecedent copies records polynomial degrees, not coefficients.

exercise 56.5.

Licensed: a fixed rank-n net u normalizes in at most Wu(n) external steps. Not licensed: a source function on a numeric input x runs in at most 3x+2 steps because its type carries that potential. The first quantity is proof-net weight at rank; the second would be input-indexed operational cost.

exercise 56.6.

Under the mutated equation, W!vm(3)=Wv(3)+1=4,W!!vm(3)=W!vm(3)+1=5. Opening the outer box may create three copies of !v, whose combined mutated weight is 34=12>5. The missing factor of X was the charge for multiplexing.

exercise 56.7.

Rank 0 exposes no copy of A, rank 1 exposes one, and rank 2 exposes two, giving weakening, dereliction, and binary contraction behavior. Each rule removes one !A on the left; none derives !!A from !A, which would be digging.

exercise 56.8.

A principal multiplicative interaction removes at least one right-logical cell of weight 1, while left cells have weight 0. For an exponential cut against rank qn, the redex charge is nWw(n)+1 and the copies cost at most qWw(n); the decrease is at least one. Commuting independent cells does not change either calculation.

exercise 56.9.

A fixed degree-3 net has bound kn3 as rank n varies. A family with degree equal to input length has a bound of the form knnn, with changing coefficient and exponent; the fixed-program hypothesis needed for one polynomial is absent.

exercise 56.10.

Linear time has degree 1 and constant space degree 0, so the theorem gives S(2)B. The construction needs a string encoding, length iterator, fixed transition net, constant-size tape/state encoding, iteration composition, and accepting-state Boolean observation.

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