Deriving Type Checkers

The relationship between a type system’s specification and the implementation of the type checker is a recurring issue when writing compilers for programming languages and it is an ongoing question if – and if so, how – the formal description of a type system can be used to support the compiler writer when implementing the type checking phase. In this paper we propose type systems formalized by constraintbased inference rules to form an ideal abstraction to accomplish the task of automatically deriving type checking functionality from them. We develop a set of algorithms employing the constraint-based flavor of the rules to perform type checks and present the design and implementation of a Haskell library utilizing these algorithms to provide functionality for the type checking phase based on the chosen abstraction

Corrigendum to: Management of Tricuspid Regurgitation: The Role of Transcatheter Therapies

Fabian Nietlispach, Michel Zuber and Francesco Maisano Heart Valve Clinic, University Hospital of Zurich, University of Zurich, Zurich, Switzerlan

Clipping of the tricuspid valve proposal of a "Rosetta Stone" nomenclature for procedural 3D transoesophageal guidance

AIMS: Although preliminary experience has shown the feasibility of tricuspid valve clipping, intraprocedural guidance remains a major issue. The aim of this report is to provide a simple nomenclature for intra-procedural 3D TEE guidance during transcatheter tricuspid valve interventions. METHODS AND RESULTS: The identification of the location of the aortic valve (AV) is fundamental to understanding the orientation of the leaflets: the leaflet opposite the AV is the posterior leaflet (P). Anterior (A) and septal (S) leaflets are easily identified counterclockwise. The movements of the guiding catheter in the right atrium can be divided for orientation: towards the AV ("Aortic" direction) or towards the posterior leaflet ("Posterior" direction); the movement perpendicular to the previous one can be towards the anterior ("Anterior" direction) or towards the septal leaflet ("Septal" direction). CONCLUSIONS: We have provided a simple nomenclature, which can be shared between the person performing the procedure and the person who is guiding, that could serve as a "Rosetta Stone" for TV clipping, and for transcatheter TV interventions in general