Records misbehaviour

Records misbehaviour

[Lukasz Stafiniak]

While I haven't encounter this in my programming, it popped out in
another thread and I think something might be done about it:

#type t1 = {fst:int;snd:int};; 
#let p1 = {fst=1; snd=2};; 
#type t2 = {snd:int};; 
#{p1 with snd=4};; 
- : t2 = {snd = 4};; 

Best Regards,
Lukasz

Re: [Caml-list] Records misbehaviour

[Jacques Garrigue]

From: Lukasz Stafiniak <lukstafi@gmail.com>

> #type t1 = {fst:int;snd:int};; 
> #let p1 = {fst=1; snd=2};; 
> #type t2 = {snd:int};; 
> #{p1 with snd=4};; 
> - : t2 = {snd = 4};; 

Indeed, this is rather counter-intuitive.
So a bug report would be welcome :-)

Note however that there is no unsoundness here: the definition of
"with" happens to be "create a record with the provided fields,
extracting omitted ones from p1". If none are omitted, which is the
case here as t2 has only one field, then p1 is currently ignored.

Jacques Garrigue

Re: [Caml-list] Records misbehaviour

[Andreas Rossberg]

Lukasz Stafiniak wrote:
> While I haven't encounter this in my programming, it popped out in
> another thread and I think something might be done about it:
> 
> #type t1 = {fst:int;snd:int};; 
> #let p1 = {fst=1; snd=2};; 
> #type t2 = {snd:int};; 
> #{p1 with snd=4};; 
> - : t2 = {snd = 4};; 

I guess this is just an instance of the following:

# type t = {a:int};;
type t = { a : int; }
# {"hi" with a=5};;
- : t = {a = 5}

-- 
Andreas Rossberg, rossberg@ps.uni-sb.de

Let's get rid of those possible thingies!  -- TB