Re: Distinguishing type names from other identifiers

[adam@irvine.com (Adam Beneschan)]

Nick Roberts wrote:

> The technique I generally use for inventing a type identifier distinct from
> identifiers I might use for objects and parameters of that type is to make
> the type identifier one step more specific (and thus, usually, longer).
>
> The justification for using a longer identifier for the type, rather than
> for the objects and parameters, is that type identifiers are generally used
> less often in practical source text.
>
> For example:
>
>    type Hour_Of_Day is range 0..23;
>    type Minute_Of_Hour is range 0..59;
>    type Seconds_Past_Minute is delta 0.001 range 0.000 .. 59.999;
>
>    function To_Seconds_Past_Midnight
>                    (Hour:    Hour_Of_Day;
>                     Minute:  Minute_Of_Day;
>                     Seconds: Seconds_Past_Minute) return Day_Duration;
>
> This example illustrates (I hope ;-) that the use of a plural or singular
> form for an identifier is not naturally to do with whether it denotes a
> type, an object, a parameter, a subprogram, or whatever, but rather with
> whatever concept it describes.  The choice of Seconds_Past_Minute is
> perhaps a little clumsy. . . .

After following this thread, and looking at this example, I really
wonder what the objection is to using _Type suffixes.  Several people
have objected to "_Type" on the ground that it doesn't add any
informational value to the name.  But do the extra words in the above
example add any value to the name, either?  I'm not convinced that
calling the type Hour_Of_Day is any more helpful to a programmer than
just calling it Hour or Hour_Type.

Of course, I could have picked a bad example to complain about, since
there could be a use for both "Minute_Of_Hour" and "Minute_Of_Day" or
"Minute_Of_Year" or "Minutes_Elapsed" types, or something like that.
But it seems to me that in many, many cases, there just isn't any
extra value to add to the name.  So *anything* you add, whether it's a
boring suffix like _Type or a boring prefix like The_, or something
less boring that appears to contain additional information as in the
above example, is still just "noise"---in essence, a kludge to keep
the compiler happy.

So if I'm right and anything you add is just noise, I think it may be
best to use a boring suffix like _Type.  The small advantage to this
is that it may make your names easier to remember.  If you use _Type
consistently, at least you have less information to carry around in
your head, instead of trying to remember something different for each
type: "Now, let's see, did I call this one _Number, or _Of_Day, or
_Of_Hour, or what?" leading to potential errors such as the one Nick
included in his above example.

                                -- Adam

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