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## Section: New Results

### Types by Need

Participants : Beniamino Accattoli, Maico Leberle.

This joint work with Giulio Guerrieri (Post-doc at Bath University) [27] develops a multi type system for call-by-need evaluation of the $ł$-calculus. The type system is obtained by combining features by well-known systems for call-by-name and call-by-value. It characterizes termination, and, moreover, its type derivations provide precise information about the number of steps to reach the result. The novelty is that, while the systems for call-by-name and call-by-value are obtained by the linear logic interpretation of these evaluation schemes, call-by-need has no linear logic interpretation.