We present a technique to prevent the construction of intermediate data structures in functional programs, which is based on results from the theory of tree transducers. We first decompose function definitions, which correspond to macro tree transducers, into smaller pieces. Under certain restrictions...

Structured documents are usually processed by tree-based document transformers, which transform the document tree representing the structure of the input document into another tree structure. Event-based document transformers, by contrast, recognize the input as a stream of parsing events, i. e. lexical tokens, and process the events one by one in an event-driven manner. Event-based document transformers have advantages that they need less memory space and that they are more tolerant of large inputs, compared to tree-based transformers, which construct the intermediate tree representation. This paper proposes an algorithm which derives an event-based transformer from a given specification of a document transformation over a tree structure. The derivation of an event-based transformer is carried out in the framework of attribute grammars. We first obtain an attribute grammar which processes a stream of parsing events, by applying a deforestation method; We then derive an attribute evaluation scheme relevant to the event-based transformation. Using this algorithm, one can develop event-based document transformers in a more declarative style than directly programming over the stream of parsing events.

Attribute grammars are well-designed to construct complex algorithms by composing several ones together. Actually, there exists a powerful transformation called descriptional composition which highly simplifies the composition of two attribute grammars by removing useless intermediate constructions. However, most of non-linear algorithms can not be expressed with attribute grammars. Thus, many compositions can not be simplified by the descriptional composition. In this paper, we present Equational Semantics, a formalism largely inspired by attribute grammars but where nonlinear algorithms can be encoded. More precisely, instead of being restricted to one input static tree as it is the case for attribute grammars, an algorithm encoded with Equational Semantics may use dynamically constructed trees. This formalism consists in an very poor abstract syntax. We present its semantics and some of its transformations such as partial evaluation and descriptional composition (also called defores...

Recently, generic programming becomes of a major interest in several programming paradigms. A recurrent idea to achieve genericity is to abstract computations from their representative data structures. This allows these generic specifications to be instantiated onto a large number of neighboring data structures. Moreover the program can be adapted when the data structures have to evolve. Polytypic programming, adaptive programming and generic attribute grammars are generic programming methods related to this approach. Their comparison leads us to propose a common framework for generic programming: automatic generation of programs that compute morphisms between data structures, and program composition. Thanks to this compositional approach, the complete specialization of generic programs could be advantageously delegated to some powerful and general deforestation method. 1 Introduction In several programming paradigms, generic programming is being emerging. When an algorithm is specifi...