Re: Strong Types ?

> I faced a question during my research on desing and implementation of
> programming language. The question arises from area of type binding
> and checking in design of programming languages. question :
> Can we call a programming language which has both static type
> checking and static type binding a strongly type programming
> language; if so why and is there any programming language with these
> characteristics.


Hi,


You might already be aware of a book by Benjamin C. Pierce titled
"Types and Programming Languages"
(http://www.cis.upenn.edu/~bcpierce/tapl/).


I am describing here in very brief, strongly typed languages has a
sound type system characterized by 2 properties: progress and
preservation. The progress is: given an expression e, it is either a
value, or the evaluation of e progresses to another expression e'. The
preservation is: if e is of type T, and evaluation of e progresses to
e', then type of e' is still T.


I understand that these 2 rules sound very abstract, but Benjamin's
book start from a very simple language examples to modeling quite
complex languages with sub-typing, but still keeping these 2 rules at
kernel. I found that amazing. People have also done type system for a
small subset of Java (Featherweight Java) which preserves OO
characteristics such as classes, inheritance, dynamic typecasts and
generics/templates (http://portal.acm.org/citation.cfm?id=503505),
perhaps you want to take a look at that.


+satish
http://vcard.acm.org/~satish.gupta

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