Re: [Caml-list] a reckless proposal

[Miles Egan <miles@caddr.com>]

On Wed, Jul 25, 2001 at 08:15:49AM -0700, Brian Rogoff wrote:
> I don't know about records, but it appears that there is work on mixin
> modules. While I agree that the record field problem is annoying, and
> definitely not a feature, it's not on my top 3 list of fixes or new 
> features desired. Probably somewhere between a petty complaint and a 
> nuisance. I do work with programmers who hate Caml for this very reason
> though!

Rejecting ocaml over this is a tragic mistake! :)  It can be very jarring to
people with the wrong expectations, as you've seen.  The two situations in which
I find it most jarring:

1. The work-around usually suggested, to wrap the record definitions in local
module definitions, is actually worse.  It results in code that looks like
var.Type.field, rather than Type.var.field.  This gives C++/Java programmers
fits.  The more cumbersome, but familiar method of prefixing field names with
the record type, a la var.type_field, is even preferrable.

This syntax appears even in common uses of the standard library.  For example,
if I use the Unix stat functions, I have to access the fields of the returned
record as res.Unix.st_perm, not just res.st_perm or even Unix.res.st_perm.  Once
the difference is clear, this isn't too annoying, but it's a big speedbump for
newbies.

> It also seems that you'd like to eliminate these false friends (good phrase, 
> especially for a bilingual French-English mailing list!) by subsuming them
> into features that mainstream programmers know well. That would be a
> mistake, since you'd end up with a mainstream language. 

I certainly wouldn't generally characterize my intentions that way.  I'm more
interested in re-evaluating gratuitous differences.  At any rate, I agree that
the loss of pattern-matching more than outweighs the benefits in this case.
Ocaml is stylistically quite comfortably out of the mainstream in many ways and
I'm sure it will remain so.

> 90s). Ada packages correspond very closely to ML modules, and there are
> even crude approximations to functors and signatures in Ada 95 (generic 
> formal package parameters in Ada parlance). 

It's not the combination of packaging and polymorphism in Ocaml that I think is
confusing.  In fact, I think it's one of it's most compelling features.  It's
the fact that compilation units are implicit top-level modules with special
properties.  A few paragraphs in the documentation explaining top-level modules
and the relationship between source files and implicit top-level modules might
clarify this a bit better for new users.

Perhaps some kind of "Ocaml for Java Programmers" FAQ might be useful?

-- 
miles

"We in the past evade X, where X is something which we believe to be a
lion, through the act of running." - swiftrain@geocities.com
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