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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Seeking for papers about tagged types vs access to subprograms
Date: Fri, 10 May 2013 21:04:42 +0300
Organization: Tidorum Ltd
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Date: 2013-05-10T21:04:42+03:00
List-Id: <comp.lang.ada>

On 13-05-10 06:29 , Yannick Duchêne (Hibou57) wrote:
> Le Fri, 10 May 2013 00:19:14 +0200, Randy Brukardt
 ...
>> Yes, because we need to move beyond typing to other forms of static error
>> detection. Typing is too rigid to do a good job -- you need to include
>> statically known information about the contents of variables and
>> parameters,
>> which can change from line-to-line in a program.
> 
> I feel the same. I often though typing can't do everything if it comes
> with value type checking, while in some occasions, I tried to express
> each validity condition with types and then type checking (that ends to
> be crazy, indeed). A simple example, is paired invocation, where
> whenever a sub‑program is is invoked, sooner or later, another
> sub‑program must be invoked too on the same argument, ex. like `Open`
> and later `Close`. This cannot be expressed with types and indeed
> requires assertions.

Are you familiar with the "typestate" concept? As I understand it, the
intent is to check state-sequence rules such as Open-followed-by-Close.
See http://en.wikipedia.org/wiki/Typestate_analysis.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .