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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Ada Quality and Style book discussion ("_Type" suffix)
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Date: Sun, 20 Nov 2005 21:43:07 +0100
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Date: 2005-11-20T21:43:06+01:00
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On Sun, 20 Nov 2005 19:41:05 GMT, Jeffrey R. Carter wrote:

> Anonymous Coward wrote:
>> Suffixes are *very* useful, as I will illustrate.  It's no coincidence
>> that well named, direct, concise type names very often match
>> (verbatim) good names for objects (including enums), in the absense of
>> a type suffix.
> 
> GOOD suffixes are very useful. _Type is a bad suffix. As AC himself says 
> elsewhere, "If you're repeating information from your declaration in your 
> identifiers, then you've created a maintenance problem by introducing too much 
> noise". "type X_Type" clearly repeats information from the declaration in the 
> identifier.

True, Hungarian notation is bad.

> Prefixes are very bad. The 1st few characters of an identifier are the most 
> important in determining what it is. If lots of identifiers start with the same 
> sequence of characters, it makes reading harder.

Yes, prefix Hungarian notation is worse than bad.

> My personal preferences are
> 
>>       type Day is (Monday, Tuesday,  Wednesday, Thursday,
> 
> Day_ID

Is Monday an ID?

>>       type Meters is new Float;
> 
> Meter_Value

Type is a value, how so?

Meter_Value is something like 1000mm, or the length of that metal bar
somewhere in Paris (I guess), or the distance traveled by light in vacuum
during a time interval of 1/299 792 458 of a second... (:-))

I would prefer

   type Metric_Distance is new Float;

if it is necessary to underline that the distance is measured in meters.

> procedure P (Speed : in Speed_Value);

   procedure P (Speed_Value : in Speed);

I presume. But better is:

   procedure P (Value : in Speed);

--------------
The problem is that both type and variable of are meant to identify the
same thing: a set of values. When an object is declared one can try to name
it in a way that would reflect the specific value it represents:

Today : Day;
Tomorrow : Day;

With subroutine parameters it gets difficult. More abstract they are more
difficult is to find a name reflecting the problem space. In the end it
becomes: Value, Index, I, J, K, X, Y, Left, Right, Result etc.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de