Variable length strings...

[thoyt@DDN-WMS.ARPA (Thomas Hoyt)]

In issue #142, D. Papay is right on the $$$ with his comments on variable
length strings.  However...

>...I suggest you remove the default expression " := 0" from your
> record type ... and always declare ... with explicit discriminant
> contraints...

If you do this, you lose all the advantages of a parameterized record,
i.e. variable length strings.  Why not constrain the subtype of the
range of the record parameter:
^^^^^
   subtype Len_range is integer range 0..256; -- or some other max
                                              -- string length

This way the compiler would know exactly how big the strings could ever
get and plan accordingly...i.e. stop complaining.

Of course, you could still have pretty huge strings without coming close to
whatever Integer'Last is.  Another advantage is that the writer of the
generic could explicitly control how big the variable length strings
could ever get, without having to rely upon implimentation details. 

You also eliminate a generic parameter, relieving the user of an unnecessary
detail.  Most text editing functions wouldn't ever need more than about
1024 chars at a time (need...hope?:-))
 

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Thomas Hoyt             |  "Government Computers for Government business..."
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