A Functional Synchronous Language with Integer Clocks

Mardi 31/03/2015, LUG, salle du bas, 10h30 (to be confirmed)

Adrien Guatto ENS Ulm/Parkas

Résumé:

Synchronous languages in the vein of Lustre are first-order functional languages dedicated to stream processing. Lustre compilers use a type-like static analysis, the clock calculus_, to reject programs that cannot be implemented as finite state machines. The broad idea is to assign to each element of a stream a logical computation date in a global, discrete time scale. When this analysis succeeds, the types obtained guide the code generation phase of the compiler, which produces transition functions. In practice, these functions consists in simple, bounded memory C code featuring only assignments and conditional statements.

This talk presents a variation on Lustre and its compilation. Our proposal is twofold. First, we add a new construct that creates a local time scale whose internal steps are invisible from the outside. Second, we change the clock calculus to allow several elements of a stream to be computed during the same time step. I will discuss the resulting type system, and how the code generation scheme of Lustre, once adapted to this new setting, generates code featuring nested loops.