2 research outputs found
Mechanisation of Model-theoretic Conservative Extension for HOL with Ad-hoc Overloading
Definitions of new symbols merely abbreviate expressions in logical
frameworks, and no new facts (regarding previously defined symbols) should hold
because of a new definition. In Isabelle/HOL, definable symbols are types and
constants. The latter may be ad-hoc overloaded, i.e. have different definitions
for non-overlapping types. We prove that symbols that are independent of a new
definition may keep their interpretation in a model extension. This work
revises our earlier notion of model-theoretic conservative extension and
generalises an earlier model construction. We obtain consistency of theories of
definitions in higher-order logic (HOL) with ad-hoc overloading as a corollary.
Our results are mechanised in the HOL4 theorem prover.Comment: In Proceedings LFMTP 2020, arXiv:2101.0283
The (In)Efficiency of interaction
Evaluating higher-order functional programs through abstract machines inspired by the geometry of the interaction is known to induce space efficiencies, the price being time performances often poorer than those obtainable with traditional, environment-based, abstract machines. Although families of lambda-terms for which the former is exponentially less efficient than the latter do exist, it is currently unknown how general this phenomenon is, and how far the inefficiencies can go, in the worst case. We answer these questions formulating four different well-known abstract machines inside a common definitional framework, this way being able to give sharp results about the relative time efficiencies. We also prove that non-idempotent intersection type theories are able to precisely reflect the time performances of the interactive abstract machine, this way showing that its time-inefficiency ultimately descends from the presence of higher-order types