Re: Display of strings by interpreter

[Andrew Janke]

On 10/23/19 2:08 PM, John W. Eaton wrote:
> On 10/23/19 1:33 PM, Rik wrote:
>> On 10/23/2019 10:29 AM, John W. Eaton wrote:
> 
>>> Yes, this seems like a good thing to do.  Also the feature request in
>>> #56974.  I would even say that we could consider displaying the type if
>>> it is double.
>>>
>>
>> Yes, it never made sense to me that Matlab would list the size and
>> type for
>> all variables except double.  Be consistent, and tell the user when it
>> is a
>> double.
>>
>>> Did you want to work on either of these?
>>>
>>
>> I'll take a look at the string display issue.
> 
> OK, I'll look at the data type thing.
> 
> In the interest of simplicity, I think we should just make these changes
> and not make them configurable.

I agree with not making them configurable. As a maintainer, type
information is important diagnostic info. If the display were
configurable, then when you got user output in a bug report, you'd
always have to wonder "is the annotation missing because this isn't a
special type, or because the user has turned off annotations?".

I think it actually makes sense to omit the type info when the displayed
type is a double. Because doubles are the standard or default type for
numeric values in Matlab/Octave: most work is done with doubles, numeric
literals produce doubles, and using a double for pretty much anything
will probably work. (And in early Matlab versions doubles were the
_only_ numeric type.) From what I've seen, the int types are rarely used
in practice, and it's int types that cause problems because M-code does
narrowing instead of widening conversions for mixed-mode arithmetic.
(Singles narrow, too; that can cause precision issues.) So why clutter
up the command window with a "double" notation when 95% of the time
that's what it's going to be, and if doubles are the only numeric type
that doesn't have a type annotation, you can still correctly infer their
type from the absence of the annotation? (And if strings are displayed
with quotes, then you can distinguish a numeric from e.g. the string
"12.345".)

Cheers,
Andrew