R devel - Jun 2017 - [WISH / PATCH] possibility to split string literals across multiple lines

> On Wed, 14 Jun 2017, G?bor Cs?rdi wrote:
>
> > I like the idea of string literals, but the C/C++ way clearly does not
> > work. The Python/Julia way might, i.e.:
> >
> > """this is a
> > multi-line
> > lineral"""
> 
> luke-tierney at uiowa.edu:
> This does look like a promising option; some more careful checking
> would be needed to make sure there aren't cases where currently
> working code would be broken.
I don't see how this proposal solves any problem of interest.

String literals can already be as long as you like.  The problem is
that they will get wrapped around in an editor (or not all be
visible), destroying the nice formatting of your program.

With the proposed extension, you can write long string literals with
short lines only if they were long only because they consisted of
multiple lines.  Getting a string literal that's 79 characters long
with no newlines (a perfectly good error message, for example) to fit
in your 80-character-wide editing window would still be impossible.

Furthermore, these Python-style literals have to have their second
and later lines start at the left edge, destroying the indentation
of your program (supposing you actually wanted to use one).

In contrast, C-style concatenation (by the parser) of consecutive
string literals works just fine for what you'd want to do in a
program.  The only thing they wouldn't do that the Python-style
literals would do is allow you to put big blocks of literal text in
your program, without having to put quotes around each line.  But
shouldn't such text really be stored in a separate file that gets
read, rather than in the program source?

   Radford Neal

On Fri, Jun 16, 2017 at 7:04 PM, Radford Neal <radford at cs.toronto.edu>
wrote:
>> On Wed, 14 Jun 2017, G?bor Cs?rdi wrote:
>>
>> > I like the idea of string literals, but the C/C++ way clearly does
not
>> > work. The Python/Julia way might, i.e.:
>> >
>> > """this is a
>> > multi-line
>> > lineral"""
>>
>> luke-tierney at uiowa.edu:
>
>> This does look like a promising option; some more careful checking
>> would be needed to make sure there aren't cases where currently
>> working code would be broken.
>
> I don't see how this proposal solves any problem of interest.
>
> String literals can already be as long as you like.  The problem is
> that they will get wrapped around in an editor (or not all be
> visible), destroying the nice formatting of your program.
>From the Python docs:
String literals can span multiple lines. One way is using
triple-quotes: """...""" or
'''...'''. End of lines are automatically
included in the string, but it?s possible to prevent this by adding a
\ at the end of the line.

[...]

Gabor

On Fri, Jun 16, 2017 at 1:14 PM, G?bor Cs?rdi <csardi.gabor at gmail.com>
wrote:
> On Fri, Jun 16, 2017 at 7:04 PM, Radford Neal <radford at
cs.toronto.edu> wrote:
>>> On Wed, 14 Jun 2017, G?bor Cs?rdi wrote:
>>>
>>> > I like the idea of string literals, but the C/C++ way clearly
does not
>>> > work. The Python/Julia way might, i.e.:
>>> >
>>> > """this is a
>>> > multi-line
>>> > lineral"""
>>>
>>> luke-tierney at uiowa.edu:
>>
>>> This does look like a promising option; some more careful checking
>>> would be needed to make sure there aren't cases where currently
>>> working code would be broken.
>>
>> I don't see how this proposal solves any problem of interest.
>>
>> String literals can already be as long as you like.  The problem is
>> that they will get wrapped around in an editor (or not all be
>> visible), destroying the nice formatting of your program.
>
> From the Python docs:
>
> String literals can span multiple lines. One way is using
> triple-quotes: """...""" or
'''...'''. End of lines are automatically
> included in the string, but it?s possible to prevent this by adding a
> \ at the end of the line.
And additionally, in Julia triple quoted strings:

Trailing whitespace is left unaltered. They can contain " symbols
without escaping. Triple-quoted strings are also dedented to the level
of the least-indented line. This is useful for defining strings within
code that is indented. For example:

Hadley

-- 
http://hadley.nz

On 16/06/2017 2:04 PM, Radford Neal wrote:
>> On Wed, 14 Jun 2017, G?bor Cs?rdi wrote:
>>
>>> I like the idea of string literals, but the C/C++ way clearly does
not
>>> work. The Python/Julia way might, i.e.:
>>>
>>> """this is a
>>> multi-line
>>> lineral"""
>>
>> luke-tierney at uiowa.edu:
>
>> This does look like a promising option; some more careful checking
>> would be needed to make sure there aren't cases where currently
>> working code would be broken.
>
> I don't see how this proposal solves any problem of interest.
>
> String literals can already be as long as you like.  The problem is
> that they will get wrapped around in an editor (or not all be
> visible), destroying the nice formatting of your program.
>
> With the proposed extension, you can write long string literals with
> short lines only if they were long only because they consisted of
> multiple lines.  Getting a string literal that's 79 characters long
> with no newlines (a perfectly good error message, for example) to fit
> in your 80-character-wide editing window would still be impossible.
>
> Furthermore, these Python-style literals have to have their second
> and later lines start at the left edge, destroying the indentation
> of your program (supposing you actually wanted to use one).
>
> In contrast, C-style concatenation (by the parser) of consecutive
> string literals works just fine for what you'd want to do in a
> program.  The only thing they wouldn't do that the Python-style
> literals would do is allow you to put big blocks of literal text in
> your program, without having to put quotes around each line.  But
> shouldn't such text really be stored in a separate file that gets
> read, rather than in the program source?
I agree with most of this, but I still don't see the need for a syntax 
change.  That's a lot of work just to avoid typing "paste0" and
some
commas in

  paste0("this is the first part",
         "this is the second part")

If the rather insignificant amount of time it takes to execute this 
function call really matters (and I'm not convinced of that), then 
shouldn't it be solved by the compiler applying constant folding to 
paste0()?

(Some syntax like r"xyz" to make it easier to type strings containing 
backslashes and quotes would actually be useful, but that's a different 
issue.)

Duncan Murdoch

> On 16 Jun 2017, at 21:17 , Duncan Murdoch <murdoch.duncan at
gmail.com> wrote:
> 
> paste0("this is the first part",
>        "this is the second part")
> 
> If the rather insignificant amount of time it takes to execute this
function call really matters (and I'm not convinced of that), then
shouldn't it be solved by the compiler applying constant folding to
paste0()?
And, of course, if it is equivalent to a literal, it can be precomputed. There
is no point in having it in the middle of a tight loop.

-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com