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Requirements for String classes
Author "Andrew C. Greenberg"
Date: Wed, 22 Sep 1999 02:09:06 -0400
Subject: Unicode support
- Strings are somewhat homogenous;
- Strings are comprised of elements of a Flyweight pattern class;
- Much of the "usual" things we do with a string are
determined by the underlying character class.
Perhaps we can study what things we really do with strings, at least
to enumerate them, and see how they matter.
Questions
What do strings do?
What must they do?
Which of the following are necessary, mandatory, or even useful? Which depend upon the class?
- support a (partial;total) linear ordering (=,<,>)
- substring
- catenation
- indexing
- collecting, selecting, allAre, someIs, based upon blocks
that are passed (conceptually) to individual objects.
- clumping and declumping (word-based, delimiter-based, token-based)
- random access out (not as special case of substring, but pulling the character object out of the class as well.
- random access in (not as special case of catentation, but
validating and/or coercing the character on the way in.
- notion and creation of a null string as identity operator for many of the preceding operations
- searching for substrings.
- sizing
I don't know that I agree with those who believe that a string must
be "growable/shrinkable" Perhaps we should consider making strings
that are length-immutable, per Python. Doing so can facilitate other
of what I have now come to think of as string-like operations, in
particular, slicing and index-shifting, by creation of proxy objects
on the original string, which share changes to the underlying
content. Size-shifting operations can be permitted, but create
copies of the original, changes to which do not impact the content of
already-taken slices.
consider also the Applescript container notion
Date: Tue, 21 Sep 1999 19:12:39 -0500
From: Joe Davison
Subject: Unicode support
I tend to agree that the root of the problem is that we lack a good abstract definition of String, and I wonder if we really can have one that's much more specific than ArrayOfCharacter. Besides the obvious
- comparisons,
- concatenation and
- substring operations
things we often like to do with strings in various languages are - pattern matching with regular expressions,
- creating token streams,
- storing them in files,
- reading them from files,
- interpreting them as a statement in some human or computer language
- ...
But most of those operations might properly be done on objects that Strings are convertible to/conformable with.
Do we really want a regular expression capability for GeneralString? -maybe so -- certainly Perl's implementation of regular expression functions on character strings is a major advantage over many other languages. I suppose one might want two methods
GeneralString>>asRegularExpression (the compiler) and
GeneralString>>match: aRegularExpression (the interpreter),
hypothesizing a RegularExpression class -- which would have to be pretty tricky with GeneralCharacter s...
joe