Subj : Re: any function to handle this kind of counting?
To   : comp.programming
From : Peter Ammon
Date : Sun Jul 31 2005 12:55 am

Jon Harrop wrote:
> Alex Fraser wrote:
> 
>>>No, that is not similar to the OCaml I posted because the OCaml programs
>>>are self-contained and either use lists (which are native to the
>>>language) or data structures found in the OCaml stdlib.
>>
>>Why does that make a difference?
> 
> 
> Having common definitions in a standard library is beneficial for many
> reasons, primarily:
> 
> 1. Stability (many relevant bits of OCaml's stdlib have been formally proven
> correct using theorem provers and will have been used by many more people
> than a "home grown" C implementation).

I'd wager that more eyes have looked at something like the GLib C data 
structure library than at OCaml.

> 
> 2. Generality (what happens if you want to combine two difference C programs
> which use two different "home grown" set implementations?).

If you want a library to support some task, you're going to find a lot 
more options in C than in OCaml.  A data structure impedance mismatch is 
easier to deal with than a language mismatch.

> 
> 3. Efficiency (a "home grown" set implementation in C is unlikely to match
> the performance of OCaml's set implementation).

Doubtful.  OCaml is very fast, but it still targets the same instruction 
set as C, and there are very fast C libraries as well.

> 4. Capability (OCaml's built-in hash function can traverse any data
> structure).

I don't understand what you mean by this.

I have great respect for OCaml, but also for C; both are powerful and 
capable languages.

For the record, here's how I'd do it in Cocoa/Objective-C, using a hash 
table:

NSMutableDictionary* dict = [NSMutableDictionary dictionary];
NSEnumerator* enumer = [input objectEnumerator];
NSString* string;
while ((string = [enumer nextObject]))
	[dict setObject:[NSNumber numberWithInt:1 + [[dict objectForKey:string] 
intValue]] forKey:string];

Certainly nothing approaching "hundreds of lines!"  If anything, it's 
shorter than the OCaml approach.

-Peter

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