Type extension through polymorphism

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Type extension through polymorphism

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ACM Transactions on Programming Languages and Systems (TOPLAS) archive
Volume 12 , Issue 1 (January 1990) table of contents

Pages: 135 - 138

Year of Publication: 1990

ISSN:0164-0925

Author

F. Warren Burton

Department of Computer Science, 3190 MEB, University of Utah, Salt Lake City, UT

Publisher

ACM New York, NY, USA

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Downloads (6 Weeks): 3, Downloads (12 Months): 38, Citation Count: 4

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abstract references cited by index terms collaborative colleagues

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ABSTRACT

A record data type can be extended by addition of more fields. The extended type is a subtype of the original, in that any value of the extended type can be regarded as a value of the original type by ignoring the additional fields. This results in a type hierarchy. Milner [3] has proposed a polymorphic type system. With the Milner approach, the type of a function may contain type variables. This also results in a type hierarchy. In a language with a polymorphic type system, if it is anticipated that a record type will need to be extended, then the record type can be defined to have a dummy extension field. In the parent type, the extension field will have null contents of type void. The type of the extension field can differ with different subtypes. The approach can be extended to allow a type to be subtype of two or more parent types. To a limited extent, this approach can be used in Ada and other languages with generic program units.

REFERENCES

Note: OCR errors may be found in this Reference List extracted from the full text article. ACM has opted to expose the complete List rather than only correct and linked references.

	1	G.M. Birtwhistle , O.J. Dahl , B. Myhrhaug , K. Nygaard, Simula Begin, Chartwell-Bratt Ltd, 1979
	2	Lalita Jategaonkar , John Mitchell, ML with extended pattern matching and subtypes, Proceedings of the 1988 ACM conference on LISP and functional programming, p.198-211, July 25-27, 1988, Snowbird, Utah, United States [doi>10.1145/62678.62702]
	3	MILNER, R. A theory of type polymorphism in programming. J. Comput. Syst. Sci. 17 (Dec. 1978), 348-375.
	4	D. A. Turner, Functional programs as executable specifications, Proc. of a discussion meeting of the Royal Society of London on Mathematical logic and programming languages, p.29-54, June 1985, London, United Kingdom
	5	D. A. Turner, Miranda: a non-strict functional language with polymorphic types, Proc. of a conference on Functional programming languages and computer architecture, p.1-16, January 1985, Nancy, France
	6	D Turner, An overview of Miranda, ACM SIGPLAN Notices, v.21 n.12, p.158-166, Dec. 1986 [doi>10.1145/15042.15053]
	7	N. Wirth, Type extensions, ACM Transactions on Programming Languages and Systems (TOPLAS), v.10 n.2, p.204-214, April 1988 [doi>10.1145/42190.46167]

CITED BY 4

	Dennis M. Volpano, Subtypes and quantification, ACM Transactions on Programming Languages and Systems (TOPLAS), v.13 n.4, p.631-632, Oct. 1991
	Oleg Kiselyov , Ralf Lämmel , Keean Schupke, Strongly typed heterogeneous collections, Proceedings of the 2004 ACM SIGPLAN workshop on Haskell, September 22-22, 2004, Snowbird, Utah, USA
	Simon Marlow, An extensible dynamically-typed hierarchy of exceptions, Proceedings of the 2006 ACM SIGPLAN workshop on Haskell, September 17-17, 2006, Portland, Oregon, USA
	Matthew Fluet , Riccardo Pucella, Phantom types and subtyping, Journal of Functional Programming, v.16 n.6, p.751-791, November 2006