Wand, M. 1989. Type inference for records concatenation and simple objects. In Proceedings of the 4th IEEE Symposium on Logic in Computer Science. IEEE, New York, 92-97.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....An alternative approach, initiated by Wand [1987; 1988] is to extend ML style polymorphic typing directly to record polymorphism. This idea was further developed in a number of type inference systems [Jategaonkar and Mitchell 1993; Ohori and Buneman 1988; 1989; R emy1989; 1992; 1994b; Wand 1989]. In these type systems, a most general polymorphic type scheme can be inferred for any typable untyped term containing operations on records. By appropriate instantiation of the inferred type scheme, an untyped term can safely be used as a value of various di erent types. This approach not only ....

....ecient compilation method that always compile out labeled eld access into a direct index operation, as we shall explain in the next subsection. In addition to record extension operations, various forms of record concatenation operations have also been proposed [Harper and Pierce 1991; R emy 1992; Wand 1989]. Inclusion of any of these operations signi cantly complicates both the type theoretical analysis and compilation. Also, it is not obvious which of these powerful operations is really needed. For example, in database programming a typical application area where labeled records play an important ....

Wand, M. 1989. Type inference for records concatenation and simple objects. In Proceedings of the 4th IEEE Symposium on Logic in Computer Science. IEEE, New York, 92-97.

....system, however, does not share ML s feature of existence of principal typing schemes (see [OB88, Wan88] for an analysis of this issue. Based on Wand s general observation, OB88] extended the notion of principal type schemes to include conditions on type variables. See also [Sta88, JM88, Rem89, Wan89] for related studies. This extension allows ML polymorphism to be extended to standard operations on records and variants and also to various database operations such as join and projection. See also [Wan89, CM89, HP91, Rem91] for proposals for other operations on records. For example, the ....

....type schemes to include conditions on type variables. See also [Sta88, JM88, Rem89, Wan89] for related studies. This extension allows ML polymorphism to be extended to standard operations on records and variants and also to various database operations such as join and projection. See also [Wan89, CM89, HP91, Rem91] for proposals for other operations on records. For example, the function increment age can be implemented by the following code: fun increment age(p) modify(p; Age ; p:Age 1) where e:l selects the l eld from the record e, and modify(p; l; e) returns the new record that ....

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M. Wand. Type inference for records concatenation and simple objects. In Proc. Symp. on Logic in Computer Science, pages 92-97, 1989. 24

....as r l. We can also de ne a function which composes two records as r 1 : r 2 :X:r 1 (r 2 X) Since we need the information about which variables are captured through the context applications, our system essentially contains the same diculty in typing as the calculi for record concatenation [18, 7, 13]. Especially, R emy [13] gives a record a type f ) 0 g where each of and 0 denotes a row of elds of labels and their types. A row may contain a row variable . For example, a : int is a row. The intuition is that a record of such type is formulated as if it were a function: given ....

M. Wand. Type inference for records concatenation and simple objects. In Proceedings of 4th IEEE Symposium on Logic in Computer Science, pages 92-97, 1989.

....a complex condition which can no longer be represented by a kind. To give a type scheme for join, we need to extend the notion of (kinded) typing schemes to conditional typing schemes [OB88] by adding syntactic conditions on instantiation of type variables. A similar problem was later observed in [Wan89] if one uses a record concatenation operation rather than join. See also [CM89, HP91] for polymorphic calculi with record concatenation. Since we are primarily concerned with database operations, our inclination is to examine the record joining operation that naturally arises as a result of ....

M. Wand. Type inference for records concatenation and simple objects. In Proceedings of 4th IEEE Symposium on Logic in Computer Science, pages 92--97, 1989.

.... sort of a set of bindings informs us concisely which identifiers are bound to known data (those whose sorts are individuals) and which are bound to unknown data (those whose sorts are proper sorts) These record sorts are similar to the record types studied by Wand, Cardelli, Mitchell and others [6, 14, 15]. The domain of each record sort must be known, i.e. there must be no variables ranging over the domain of a record sort. We can use record sorts to represent the sorts of bindings, during sort inference of a particular action, since the domain of each set of bindings (a set of identifiers) will ....

....While record sorts can be used to specify the sorts of individual actions, they are not sufficient to describe sort inference over actions. For this, we need to extend the record sorts into record sort schemes. This extension follows the extension of record types into record schemes by Wand [15]. We extend the notation as follows. We extend sorts to sort schemes which include sort variables, denoted by , which range over sorts. Also, instead of mapping field names to sorts directly, record sort schemes map names to field schemes. A field scheme can be: a sort scheme, oe, indicating that ....

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M. Wand. Type inference for record concatenation and simple objects. In Proceedings of the 4th IEEE Symposium on Logic in Computer Science, 1989.

....Readership This thesis deals with the problem of sort (or type) inference in action notation. As such, we assume that the reader is familiar with the related problem of type inference in declarative programming languages. This work also makes extensive use of the record types introduced by Wand[Wan87,Wan89] (and others) and some prior knowledge would be beneficial. Finally, this thesis cannot give more than a brief introduction to the subject of action semantics. For more information, the reader is directed to [Wat90,Mos92] 1.4.2 Organization The remainder of this thesis is structured as follows: ....

.... sort of a set of bindings informs us concisely which identifiers are bound to known data (those whose sorts are individuals) and which are bound to unknown data (those whose sorts are proper sorts) These record sorts are similar to the record types studied by Wand, Cardelli, Mitchell and others [CM89,Wan87,Wan89]. The domain of each record sort must be known, i.e. there must be no variables ranging over the domain of a record sort. We can use record sorts to represent the sorts of bindings of a particular action, since the domain of each set of bindings (a set of identifiers) will be known statically. ....

M. Wand. Type inference for record concatenation and simple objects. In Proceedings of the 4th IEEE Symposium on Logic in Computer Science, pages 92--97, 1989.

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M. Wand. Type inference for record concatenation and simple objects. Fourth IEEE Symposium on Logic in Computer Science, 1989, pp. 92--97. A Subtyping recursive types We use the higher-order iterators to derive a standard inference rule about subtyping. Recall the definition

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