A new NMR signal assignment of the twenty-two carbon atoms of colchicine is proposed that differs considerably from that of Singh, Palmar, Stenberg and Farnum [Spectroscopy Letters, 10, 1001 (1977)]. Some reasons of those discrepancies are analyzed.

The CIL compiler for core Standard ML compiles whole ML programs using a novel typed intermediate language that supports the generation of type-safe customized data representations. In this paper, we present empirical data comparing the relative efficacy of several different flow-based customization strategies for function representations. We develop a cost model to interpret dynamic counts of operations required for each strategy. In this cost model, customizing the representation of closed functions gives a 12-17% improvement on average over uniform closure representations, depending on the layout of the closure. We also present data on the relative effectiveness of various strategies for reducing representation pollution, i.e., situations where flow constraints require the representation of a value to be less efficient than it would be in ideal circumstances. For the benchmarks tested and the types of representation pollution detected by our compiler, the pollution removal strategies we consider often cost more in overhead than they gain via enabled customizations. Notable exceptions are selective defunctionalization, a function representation strategy that often achieves significant customization benefits via aggressive pollution removal, and a simple form of flow-directed inlining, in which pollution removal allows multiple functions to be inlined at the same call site.

We introduce a class of semantic domains, weak powerdomains , that are intended to serve as value spaces for abstract interpretations in which safety is a concern. We apply them to the analysis of PCF programs. In the classical abstract interpretation approach, abstract domains are constructed explicitly and the abstract semantics is then related to the concrete semantics. In the approach presented here, abstract domains are derived directly from concrete domains. The conditions for deriving the domains are intended to be as general as possible while still guaranteeing that the derived domain has sufficient structure so that it can be used as a basis for computing correct information about the concrete semantics. We prove three main theorems, the last of which ensures the correctness of abstract interpretation of PCF programs given safe interpretations of the constants. This generalizes earlier results obtained for the special case of strictness analysis.

We introduce an annotated type system for a compiler intermediate language. The type system is designed to support inter-procedural register allocation and the representation of tuples and variants directly in the register file. We present an algorithm that generates constraints for assigning annotations, and prove its soundness with respect to the type system.