Haskell's overlooked object system

@misc{citeulike:316837, abstract = {Haskell provides type-class-bounded and parametric polymorphism as opposed to subtype polymorphism of object-oriented languages such as Java and OCaml. It is a contentious question whether Haskell 98 without extensions, or with common extensions, or with new extensions can fully support conventional object-oriented programming with encapsulation, mutable state, inheritance, overriding, statically checked implicit and explicit subtyping, and so on. We systematically substantiate that Haskell 98, with some common extensions, supports all the conventional OO features plus more advanced ones, including first-class lexically scoped classes, implicitly polymorphic classes, flexible multiple inheritance, safe downcasts and safe co-variant arguments. Haskell indeed can support width and depth, structural and nominal subtyping. We address the particular challenge to preserve Haskell's type inference even for objects and object-operating functions. The OO features are introduced in Haskell as the OOHaskell library. OOHaskell lends itself as a sandbox for typed OO language design.}, author = {Kiselyov, Oleg and L\"{a}mmel, Ralf }, citeulike-article-id = {316837}, eprint = {cs.PL/0509027}, keywords = {functional-programming, haskell, objects, polymorphism, subtyping, type-classes, types}, month = {Sep}, posted-at = {2005-09-13 14:16:56}, priority = {2}, title = {Haskell's overlooked object system}, url = {http://arxiv.org/abs/cs.PL/0509027}, year = {2005} }

TY - ELEC ID - citeulike:316837 L3 - citeulike-article-id:316837 TI - Haskell's overlooked object system N2 - Haskell provides type-class-bounded and parametric polymorphism as opposed to subtype polymorphism of object-oriented languages such as Java and OCaml. It is a contentious question whether Haskell 98 without extensions, or with common extensions, or with new extensions can fully support conventional object-oriented programming with encapsulation, mutable state, inheritance, overriding, statically checked implicit and explicit subtyping, and so on. We systematically substantiate that Haskell 98, with some common extensions, supports all the conventional OO features plus more advanced ones, including first-class lexically scoped classes, implicitly polymorphic classes, flexible multiple inheritance, safe downcasts and safe co-variant arguments. Haskell indeed can support width and depth, structural and nominal subtyping. We address the particular challenge to preserve Haskell's type inference even for objects and object-operating functions. The OO features are introduced in Haskell as the OOHaskell library. OOHaskell lends itself as a sandbox for typed OO language design. KW - functional-programming KW - haskell KW - objects KW - polymorphism KW - subtyping KW - type-classes KW - types AU - Kiselyov, Oleg AU - Lämmel, Ralf PY - 2005/Sep/10/ UR - http://arxiv.org/abs/cs.PL/0509027 ER -