Doo bee doo bee doo

We explore the design and implementation of Frank, a strict functional programming language with a bidirectional effect type system designed from the ground up around a novel variant of Plotkin and Pretnar's effect handler abstraction. Effect handlers provide an abstraction for modular effectful programming: a handler acts as an interpreter for a collection of commands whose interfaces are statically tracked by the type system. However, Frank eliminates the need for an additional effect handling construct by generalising the basic mechanism of functional abstraction itself. A function is but the special case of a Frank operator that interprets no commands. Moreover, Frank's operators can be multihandlers which simultaneously interpret commands from several sources at once, without disturbing the direct style of functional programming with values. Effect typing in Frank employs a novel form of effect polymorphism which avoids mentioning effect variables in source code. This is achieved by propagating an ambient ability inwards, rather than accumulating unions of potential effects outwards. With the ambient ability describing the effects that are available at a certain point in the code, it can become necessary to reconfigure access to the ambient ability. A primary goal is to be able to encapsulate internal effects, eliminating a phenomenon we call effect pollution. Moreover, it is sometimes desirable to rewire the effect flow between effectful library components. We propose adaptors as a means for supporting both effect encapsulation and more general rewiring. Programming with effects and handlers is in its infancy. We contribute an exploration of future possibilities, particularly in combination with other forms of rich type systems

Drawing machines, bathing machines, motorbikes, the stars…: where are the masterpieces?

The term ‘digital drawing’ may imply a special kind of drawing, set against a natural approach. Previous generations also had to adjust to the new technologies of the time. Some resisted, some went ahead. New methods present difficulties as well as opportunities. The how-to-draw books of the 1900’s show not just one ‘traditional’ approach, but a wide range, and a healthy debate. For the past two centuries such books have here and there discussed both drawing machines, and the connected question of how to draw machines. One way or another the world of drawing will absorb the impact of computers, and it won’t be just as an isolated genre of slightly weird drawing. So it is wrong to exclude ‘digital’ drawing from surveys, to think of this category as distinct from mainstream drawing. Museums have already collected the significant works, and traced the history. The way forward should be to integrate digital tools within the broad spectrum of drawing types. There are no good reasons for not using digital devices, and no good reasons for not using pencils. All the same, I cite three cases where a pencil and paper technique would not be up to the job: football, a drawing jam session, and astronomy

The Zoo Keeper's Paradox

Default reasoning is a mode of commonsense reas(Miing which lets us jump to plausible conclusions when there is no contrary information. A crucial operation of default reasoning systems is the checking and maintaining of consistency. However, it has been argued that default reasoning is inconsistent: Any rational agent will believe that it has some false beliefs. By doing so. the agent guarantees itself an inconsistent belief set (Israel, 1980). Perlis (1986) develops Israel's argument into an argument for the inconsist^cy of recoUective Socratic default reasoning systems. The Zoo Keeper's Paradox has been offered as a concrete example to demonstrate the inconsistency of commonsense beliefs. In this paper, w e show that Israel and Perils' arguments are not well founded. A rational agent only needs to believe that some of its beliefs are possibly or probably false. This requirement does not imply that the beliefs of rational agents are necessarily inconsistent Decision theory is used to show that concrete examples of seemingly inconsistent beliefs, such as the Zoo Keeper's Paradox, can be rational as well as consistent. These examples show that analyses of commonsense beliefs can be very misleading when utility is ignored. W e also examine the justifications of the exploratory and incredulous approaches in default reasoning, decision theoretic considerations favor the exploratory approach

Pharmacological evaluation of bee venom and melittin

AbstractThe objective of this study was to identify the pharmacological effects of bee venom and its major component, melittin, on the nervous system of mice. For the pharmacological analysis, mice were treated once with saline, 0.1 or 1.2mg/kg of bee venom and 0.1mg/kg of melittin, subcutaneously, 30min before being submitted to behavioral tests: locomotor activity and grooming (open-field), catalepsy, anxiety (elevated plus-maze), depression (forced swimming test) and apomorphine-induced stereotypy. Haloperidol, imipramine and diazepam were administered alone (positive control) or as a pre-treatment (haloperidol). The bee venom reduced motor activity and promoted cataleptic effect, in a similar manner to haloperidol. These effects were decreased by the pretreatment with haloperidol. Both melittin and bee venom decreased the apomorphine-induced stereotypies. The data indicated the antipsychotic activity of bee venom and melittin in a murine model

On the evolution of the spatial distribution of employment in postwar United States

In this paper, the authors document a pronounced trend toward deconcentration of metropolitan employment during the postwar period in the United States. The employment share of initially more dense metro areas declined and those of initially less dense metro areas rose. Motivated by this finding, the authors develop a system-of-cities model in which increase in aggregate metropolitan employment causes employment to shift in favor of less dense metro areas because congestion costs increase more rapidly for the initially more dense metro areas. A calibrated version of the model shows that the more-than-twofold increase in employment experienced by MSAs during the postwar period was indeed a powerful force favoring deconcentration.Employment (Economic theory)