Dataflow languages allow the specification of reactive systems by mutually recursive stream equations, functions, and boolean activation conditions called clocks. Lustre and Scade are dataflow languages for programming embedded systems. Dataflow programs are compiled by a succession of passes. This article focuses on the normalization pass which rewrites programs into the simpler form required for code generation. Vélus is a compiler from a normalized form of Lustre to CompCert’s Clight language. Its specification in the Coq interactive theorem prover includes an end-to-end correctness proof that the values prescribed by the dataflow semantics of source programs are produced by executions of generated assembly code. We describe how to extend Vélus with a normalization pass and to allow subsampled node inputs and outputs. We propose semantic definitions for the unrestricted language, divide normalization into three steps to facilitate proofs, adapt the clock type system to handle richer node definitions, and extend the end-to-end correctness theorem to incorporate the new features. The proofs require reasoning about the relation between static clock annotations and the presence and absence of values in the dynamic semantics. The generalization of node inputs requires adding a compiler pass to ensure the initialization of variables passed in function calls.

Introduction: Chest pain is a common main complaint in the emergency department. Among its associated differential diagnoses, pulmonary embolism remains a key concern for the clinician. There are no clear recommendations on which patients should have a formal workup for pulmonary embolism diagnosis. The objective of this study was to determine the proportion of patients with chest pain who were investigated for pulmonary embolism diagnosis and to determine the clinical profile of these patients. Methods: This was a retrospective multicenter study conducted in three French Emergency Departments. We included all patients who presented to these centers for chest pain during a 2-month period. The primary outcome was the initiation of pulmonary embolism workup. We also aimed to find factors associated with this outcome. Results: We included 881 patients with a main complaint of chest pain. Mean age was 50 years and 481 (56%) were men. A total of 263 patients (30%, 95% confidence interval 27–33%) had a formal pulmonary embolism workup, and pulmonary embolism was ultimately diagnosed in 7 cases (prevalence of 2.6%, 95% confidence interval 1.1–5.3%). Five factors were identified as independently associated with a workup for pulmonary embolism diagnosis: female sex, young age, no ischemic heart disease, recent flight and associated dyspnea. Conclusion: Among patients presenting to emergency department with chest pain, 30% had a workup for pulmonary embolism. We report five clinical variables independently associated with a higher probability of pulmonary embolism workup in our sample.