Arg-module: Float-Args also accept integer values

Arg-module: Float-Args also accept integer values

[Oliver Bandel]

Is this a wanted behaviour?
It's an implicit conversion from the integer value in the cli-string
to float. Even if this is very convenient for a user, it is not
completely following OCaml's philosophy (regarding types).

Any idea on this?!

Ciao,
   Oliver

Re: [Caml-list] Arg-module: Float-Args also accept integer values

[William D. Neumann]

On Tue, 8 Aug 2006, Oliver Bandel wrote:

> Is this a wanted behaviour?
> It's an implicit conversion from the integer value in the cli-string
> to float. Even if this is very convenient for a user, it is not
> completely following OCaml's philosophy (regarding types).

Not really.  It's the same behavior as float_of_string (because it uses 
float of string).

# float_of_string "42";;
- : float = 42.

William D. Neumann

---

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children to these tigers.  We don't need them, we're not doing 
anything with them.

Tigers are noble and sleek; children are loud and messy."

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 	-- Black Box Recorder

Re: [Caml-list] Arg-module: Float-Args also accept integer values

[Oliver Bandel]

On Tue, Aug 08, 2006 at 03:19:15PM -0600, William D. Neumann wrote:
> On Tue, 8 Aug 2006, Oliver Bandel wrote:
> 
> >Is this a wanted behaviour?
> >It's an implicit conversion from the integer value in the cli-string
> >to float. Even if this is very convenient for a user, it is not
> >completely following OCaml's philosophy (regarding types).
> 
> Not really.  It's the same behavior as float_of_string (because it uses 
> float of string).
> 
> # float_of_string "42";;
> - : float = 42.
> 
[...]

Ah, ok, I see.

Thanks!

(But.... shouldn't throw this an eception, because it's
 an int, not a float?!)

Ciao,
   Oliver

Re: [Caml-list] Arg-module: Float-Args also accept integer values

[Sachin Shah]

On 8/8/06, Oliver Bandel <oliver@first.in-berlin.de> wrote:
> On Tue, Aug 08, 2006 at 03:19:15PM -0600, William D. Neumann wrote:
> > On Tue, 8 Aug 2006, Oliver Bandel wrote:
> >
> > >Is this a wanted behaviour?
> > >It's an implicit conversion from the integer value in the cli-string
> > >to float. Even if this is very convenient for a user, it is not
> > >completely following OCaml's philosophy (regarding types).
> >
> > Not really.  It's the same behavior as float_of_string (because it uses
> > float of string).
> >
> > # float_of_string "42";;
> > - : float = 42.
> >
> [...]
>
> Ah, ok, I see.
>
> Thanks!
>
> (But.... shouldn't throw this an eception, because it's
>  an int, not a float?!)
>
> Ciao,
>    Oliver

No, because 42 is a valid int and a valid float.  Since integers are a
proper subset of floating-point numbers, this is the correct behavior
for float_of_string.

Regards,

Sachin.

Re: [Caml-list] Arg-module: Float-Args also accept integer values

[Oliver Bandel]

On Tue, Aug 08, 2006 at 02:40:58PM -0700, Sachin Shah wrote:
> On 8/8/06, Oliver Bandel <oliver@first.in-berlin.de> wrote:
> >On Tue, Aug 08, 2006 at 03:19:15PM -0600, William D. Neumann wrote:
> >> On Tue, 8 Aug 2006, Oliver Bandel wrote:
> >>
> >> >Is this a wanted behaviour?
> >> >It's an implicit conversion from the integer value in the cli-string
> >> >to float. Even if this is very convenient for a user, it is not
> >> >completely following OCaml's philosophy (regarding types).
> >>
> >> Not really.  It's the same behavior as float_of_string (because it uses
> >> float of string).
> >>
> >> # float_of_string "42";;
> >> - : float = 42.
> >>
> >[...]
> >
> >Ah, ok, I see.
> >
> >Thanks!
> >
> >(But.... shouldn't throw this an eception, because it's
> > an int, not a float?!)
> >
> >Ciao,
> >   Oliver
> 
> No, because 42 is a valid int and a valid float.  Since integers are a
> proper subset of floating-point numbers, this is the correct behavior
> for float_of_string.
> 
[...]

===========================================
first:~ oliver$ ocaml
        Objective Caml version 3.09.2

# let floatingpoint_id (x:float) = x;;
val floatingpoint_id : float -> float = <fun>
# floatingpoint_id 42;;
This expression has type int but is here used with type float
# 
===========================================

Ciao,
   Oliver

Re: [Caml-list] Arg-module: Float-Args also accept integer values

[Jonathan Roewen]

> ===========================================
> first:~ oliver$ ocaml
>         Objective Caml version 3.09.2
> 
> # let floatingpoint_id (x:float) = x;;
> val floatingpoint_id : float -> float = <fun>
> # floatingpoint_id 42;;
> This expression has type int but is here used with type float
> # 
> ===========================================

float_of_string doesn't use the ocaml type system ;-) Don't know about 
impl details, but it's basically like atof (or whatever it's called) in 
standard C libs. The two are completely separate.

Jonathan

Re: [Caml-list] Arg-module: Float-Args also accept integer values

[Jonathan Roewen]

> > ===========================================
> > first:~ oliver$ ocaml
> >         Objective Caml version 3.09.2
> > 
> > # let floatingpoint_id (x:float) = x;;
> > val floatingpoint_id : float -> float = <fun>
> > # floatingpoint_id 42;;
> > This expression has type int but is here used with type float
> > # 
> > ===========================================
> 
> float_of_string doesn't use the ocaml type system ;-) Don't know 
> about 
> impl details, but it's basically like atof (or whatever it's called) 
> in 
> standard C libs. The two are completely separate.

Oops, I should clarify: float_of_string doesn't use the ocaml lexing 
tools that are used in the toplevel, and the compilers themselves. 
That's why it parses integers.

Jonathan

Re: [Caml-list] Arg-module: Float-Args also accept integer values

[Oliver Bandel]

On Tue, Aug 08, 2006 at 08:25:42PM -0700, Jonathan Roewen wrote:
> > ===========================================
> > first:~ oliver$ ocaml
> >         Objective Caml version 3.09.2
> > 
> > # let floatingpoint_id (x:float) = x;;
> > val floatingpoint_id : float -> float = <fun>
> > # floatingpoint_id 42;;
> > This expression has type int but is here used with type float
> > # 
> > ===========================================
> 
> float_of_string doesn't use the ocaml type system ;-) Don't know about 
> impl details, but it's basically like atof (or whatever it's called) in 
> standard C libs. The two are completely separate.

I don't care about the implementation-details here,
and both ways of converting would make sense, IMHO.
But I want to have clear why this atof-like way was choosen.
So, it's a  design-decision-question (and one that could
reference to a bug, if the OCaml's type-system way was,
what initially was intended, but not implemented (for some reason).


To use the notation of OCaml's type system also for the connection with
the outer world could be one first step to have a more consistent way
of type system.

The same situation arises with database interfaces. If one uses the typical
way of connecting to databayses (e.g. sending SQL-statements of any possible
SQL (if syntactically correct)) this means that the type system breaks at
the boundary from in- to outside of the program.

IMHO it could make sense to have a limited set of SQL-statements, but that
they provide a consistent way of OCaml's types to the outer world.

And this could also be done when interfacing via command line interface.


Ciao,
   Oliver

Re: [Caml-list] Arg-module: Float-Args also accept integer values

[Jonathan Roewen]

> I don't care about the implementation-details here,
> and both ways of converting would make sense, IMHO.
> But I want to have clear why this atof-like way was choosen.
> So, it's a  design-decision-question (and one that could
> reference to a bug, if the OCaml's type-system way was,
> what initially was intended, but not implemented (for some reason).

Okay then. How about usability? Do you want your end-users to be picky
over adding a decimal point in order to provide a floating point arg?

The decimal point requirement is for the programmers, not the users;
therefore, the float_of_string design is sensible.

w.r.t the sql example, it is possible (cf. linq for C#, or one of
those pgocaml libs which does compile time checking of sql queries).

Jonathan