If T[new] is the container for T[], then what is the container for T[U]?

[Robert Jacques]

On Sat, 25 Apr 2009 20:17:00 -0400, Unknown W. Brackets  
<unknown at simplemachines.org> wrote:

> Let me say it a different way:
>
> split() returns results that are, often, stored or compared.  It is not  
> often that these results are concatenated to or modified.  Possibly,  
> they may not be sliced (further) often either.
>
> Such a case represents a perfect example of an array (or string) that  
> need not have a greater capacity than its length.  Indeed; no property  
> of the array is likely to change - its length, contents, capacity, or  
> even ptr.  All are likely to remain constant until the object is deleted  
> from memory.
>
> So, it would seem to me, this return value (as a quick example) could  
> easily be changed to one that fits the following:
>
> 1. Is an array of data.
> 2. Does not have mutable contents (data.)
> 3. Does not allow its length or capacity to be extended (excuse me for  
> considering this mutation.)
> 4. Is a reference, rather than a static array.
>
> My suggestion is that "char[]" should _be_ a StringBuilder, and "int[]"  
> should _be_ an ArrayBuilder, and we should adopt a separate syntax for  
> something that _isn't_ one of those.
>
> That said, I did just browse some of my D source files - an XML 1.0  
> parser/tree and a custom rfc-compliant ftp server - and nearly the only  
> concatenation I use is building exception strings.  I'm a little  
> surprised.  Only a couple times do I do anything a builder would be  
> useful for.
>
> One time is on XML child nodes; since I'm building a list of children,  
> it is a "builder" type thing.  However, my XML tree is fully incremental  
> - that means you could traverse it before all of the data has been read  
> from the net.  It would not be practical for me to use a builder that  
> didn't have proper read access for this case.
>
> I really think using a "StringBuilder" class is just like the solution  
> of using a "String" class.  D, in my opinion, proved the latter was not  
> necessary; I hold that the former isn't either.
>
> -[Unknown]

Okay, I understand where you're coming from. Here are some counter-points
1) Immutable strings are often concatenated, which you don't address
2) int[], real[], and basically anything not a string rarely concatenates,  
but often mutable, which you don't address
3) Rather large thread a while ago concluded the builder overhead was too  
high for general use.
4) You're proposal makes immutable char[] and char[] have different  
underlying representations.