Re: [Caml-list] Modules and record fields

[Gabriel Scherer <gabriel.scherer@gmail.com>]

The presence or absence of a warning is unrelated to whether it's a
local module or a separate file. Solarized.orange.r and
Solarized.(orange.r) are not equivalent. Solarized.orange.r means that
you access the field "r" (in the current scope) of the value
Solarized.orange. Solarized.(orange.r) opens Solarized locally for
both the resolution of the "orange" identifier and "r" field name.
Your new version is equivalent (Solarized's opening scope is even
wider).

The warning comes from the fact that since 4.01, OCaml can resolve a
field name not only by having its path given from the current scope
(eg. Solarized.r), but also by reasoning on the type of the record
value, even if the field name itself is not in scope. Accessing field
names that are not in scope is considered bad practice, hence the
warning (which is disabled by a few people that like this style).

On Sun, May 25, 2014 at 2:46 PM, Ollie Frolovs
<ollie.frolovs.2012@my.bristol.ac.uk> wrote:
> It does, but I am rather disturbed by the compiler warning. I usually aim not to have them, particularly when I am new to the language, assuming that they at least hint at unsafe programming techniques.
>
> Update: I’ve put Solarized interface and definitions into separate files (rather than having both as module Solarized = … in the main file)  and there is no warning anymore for some reason. Unless there is something else I’m doing differently without realising it.
>
> I suppose that solves my problem. Thanks everybody!
>
> solarize.mli:
>
> type colour = {r:int; g:int;  b:int}
> val base03 : colour
> val orange : colour
>
> (* END *)
>
> solarize.ml:
>
> type colour = {r:int; g:int;  b:int}
> let base03 = {r=0x00; g=0x2b; b=0x36}
> let orange = {r=0xcb; g=0x4b; b=0x16}
>
> (* END *)
>
> main.ml:
>
> …
> Solarized.(Sdl.set_render_draw_color ren orange.r orange.g orange.b 0xff)
> …
> (* END *)
>
>
> On 25 May 2014, at 11:59, Gabriel Kerneis <gabriel@kerneis.info> wrote:
>
>> On Sun, May 25, 2014 at 11:30:20AM +0100, Ollie Frolovs wrote:
>>> let module S = Solarized in
>>> Sdl.set_render_draw_color ren S.orange.r S.orange.g S.orange.b 0xff
>>> (* etc etc *)
>>
>> Doesn't this work with the latest version of the compiler? (with a
>> warning "r is not visible in the current scope, and will not be
>> selected if the type becomes unknown")
>>
>> --
>> Gabriel
>
>
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