How do you format date-times in RFC 3339 style?

How do you format date-times in RFC 3339 style?

[sirgazil]

Hi,

I'm generating atom feeds from SXML that don't validate because of the 
date-time format I'm using:

 > (use-modules (srfi srfi-19))
 > (date->string (current-date) "~Y-~m-~dT~H:~M.~S~z")
$1 = "2019-02-11T13:42.57-0500"

String $1 is close to the RFC 3339 style,¹ which is the required format 
for atom feeds, but the time zone offset should be -05:00, and Guile's 
SRFI-19 ~z time zone escape is RFC 822 style, which formats the time 
zone offset as -0500.

What should I do to get the offset in the required format?


Thanks,


_____

1. http://www.faqs.org/rfcs/rfc3339.html


-- 
Luis Felipe López Acevedo
http://sirgazil.bitbucket.io/

Re: How do you format date-times in RFC 3339 style?

[Nala Ginrut]

Hi there!
Guile web module has provided an unexpected API for that:

(define write-date (@@ (web http) write-date))

sirgazil <sirgazil@zoho.com> 于 2019年2月12日周二 03:18写道：

> Hi,
>
> I'm generating atom feeds from SXML that don't validate because of the
> date-time format I'm using:
>
>  > (use-modules (srfi srfi-19))
>  > (date->string (current-date) "~Y-~m-~dT~H:~M.~S~z")
> $1 = "2019-02-11T13:42.57-0500"
>
> String $1 is close to the RFC 3339 style,¹ which is the required format
> for atom feeds, but the time zone offset should be -05:00, and Guile's
> SRFI-19 ~z time zone escape is RFC 822 style, which formats the time
> zone offset as -0500.
>
> What should I do to get the offset in the required format?
>
>
> Thanks,
>
>
> _____
>
> 1. http://www.faqs.org/rfcs/rfc3339.html
>
>
> --
> Luis Felipe López Acevedo
> http://sirgazil.bitbucket.io/
>
>
>
>

Re: How do you format date-times in RFC 3339 style?

[Nala Ginrut]

Sorry for typo from input corrector:
s/unexpected/unexport

Nala Ginrut <nalaginrut@gmail.com> 于 2019年2月12日周二 05:39写道：

> Hi there!
> Guile web module has provided an unexpected API for that:
>
> (define write-date (@@ (web http) write-date))
>
> sirgazil <sirgazil@zoho.com> 于 2019年2月12日周二 03:18写道：
>
>> Hi,
>>
>> I'm generating atom feeds from SXML that don't validate because of the
>> date-time format I'm using:
>>
>>  > (use-modules (srfi srfi-19))
>>  > (date->string (current-date) "~Y-~m-~dT~H:~M.~S~z")
>> $1 = "2019-02-11T13:42.57-0500"
>>
>> String $1 is close to the RFC 3339 style,¹ which is the required format
>> for atom feeds, but the time zone offset should be -05:00, and Guile's
>> SRFI-19 ~z time zone escape is RFC 822 style, which formats the time
>> zone offset as -0500.
>>
>> What should I do to get the offset in the required format?
>>
>>
>> Thanks,
>>
>>
>> _____
>>
>> 1. http://www.faqs.org/rfcs/rfc3339.html
>>
>>
>> --
>> Luis Felipe López Acevedo
>> http://sirgazil.bitbucket.io/
>>
>>
>>
>>

Re: How do you format date-times in RFC 3339 style?

[sirgazil]

Hi, Nala :)


El 11/02/19 a las 4:39 p. m., Nala Ginrut escribió:
> Hi there!
> Guile web module has provided an unexpected API for that:
> 
> (define write-date (@@ (web http) write-date))


I think I prefer using public procedures, so I'll leave the error there 
for now.

But I'm curious, how do you get the time zone offset using `write-date`?


 > (use-modules (srfi srfi-19))
 >
 > (define write-date (@@ (web http) write-date))
 > (call-with-output-string (lambda (port) (write-date (current-date) 
port)))
$1 = "Tue, 12 Feb 2019 14:23:52 GMT"

I was hoping `write-date` would write the date/time in RFC 3339 format 
(https://tools.ietf.org/html/rfc3339#section-5.8).


> sirgazil <sirgazil@zoho.com <mailto:sirgazil@zoho.com>> 于 2019年2月12日 
> 周二 03:18写道：
> 
>     Hi,
> 
>     I'm generating atom feeds from SXML that don't validate because of the
>     date-time format I'm using:
> 
>       > (use-modules (srfi srfi-19))
>       > (date->string (current-date) "~Y-~m-~dT~H:~M.~S~z")
>     $1 = "2019-02-11T13:42.57-0500"
> 
>     String $1 is close to the RFC 3339 style,¹ which is the required format
>     for atom feeds, but the time zone offset should be -05:00, and Guile's
>     SRFI-19 ~z time zone escape is RFC 822 style, which formats the time
>     zone offset as -0500.
> 
>     What should I do to get the offset in the required format?
> 
> 
>     Thanks,
> 
> 
>     _____
> 
>     1. http://www.faqs.org/rfcs/rfc3339.html
> 
> 
>     -- 
>     Luis Felipe López Acevedo
>     http://sirgazil.bitbucket.io/
> 
> 
> 

-- 
Luis Felipe López Acevedo
http://sirgazil.bitbucket.io/

Re: How do you format date-times in RFC 3339 style?

[Nala Ginrut]

Sorry for the misleading, what I thought is RFC1123. Please ingnore my
answer. :-(

Re: How do you format date-times in RFC 3339 style?

[sirgazil]

El 12/02/19 a las 11:18 a. m., Nala Ginrut escribió:
> Sorry for the misleading, what I thought is RFC1123. Please ingnore my 
> answer. :-(

Ha ha, no problem, Nala :)

-- 
Luis Felipe López Acevedo
http://sirgazil.bitbucket.io/

Re: How do you format date-times in RFC 3339 style?

[Ricardo Wurmus]

sirgazil <sirgazil@zoho.com> writes:

> El 11/02/19 a las 4:39 p. m., Nala Ginrut escribió:
>> Hi there!
>> Guile web module has provided an unexpected API for that:
>>
>> (define write-date (@@ (web http) write-date))
>
>
> I think I prefer using public procedures, so I'll leave the error
> there for now.

I suppose you could hack your way around this:

(use-modules (srfi srfi-19))
(let* ((now (current-date))
       (tz  (date->string now "~z")))
 (string-append (date->string now "~Y-~m-~dT~H:~M.~S")
                (string-drop-right tz 2) ":" (string-take-right tz 2)))

What do you think?

-- 
Ricardo

Re: How do you format date-times in RFC 3339 style?

[sirgazil]

El 12/02/19 a las 11:50 a. m., Ricardo Wurmus escribió:
> 
> sirgazil <sirgazil@zoho.com> writes:
> 
>> El 11/02/19 a las 4:39 p. m., Nala Ginrut escribió:
>>> Hi there!
>>> Guile web module has provided an unexpected API for that:
>>>
>>> (define write-date (@@ (web http) write-date))
>>
>>
>> I think I prefer using public procedures, so I'll leave the error
>> there for now.
> 
> I suppose you could hack your way around this:
> 
> (use-modules (srfi srfi-19))
> (let* ((now (current-date))
>         (tz  (date->string now "~z")))
>   (string-append (date->string now "~Y-~m-~dT~H:~M.~S")
>                  (string-drop-right tz 2) ":" (string-take-right tz 2)))
> 
> What do you think?


Well, I was trying to avoid that hoping to find an obscure RFC 3339 
module or something first... But thanks, Ricardo :)


-- 
Luis Felipe López Acevedo
http://sirgazil.bitbucket.io/

How do you format date-times in RFC 3339 style?

[tantalum]

i once wrote a rfc3339 reader/writer and worked through some gotchas, maybe the code contains hints that are helpful.
for example, here is a function that converts from a timestamp to a rfc3339 date string:

   (define* (utc->rfc3339 a #:optional (offset 0) (seconds-fraction 0))
     "integer:posix-time -> string"
     (let
       ( (date-time
           (let (t (gmtime (+ a offset)))
             (apply
               (l (y m d h mi s)
                 (string-append y "-"
                   m "-"
                   d "T"
                   h ":"
                   mi ":"
                   s
                   (if (zero? seconds-fraction) ""
                     (string-append "." (number->string seconds-fraction)))))
               (map number->padded-string
                 (list (+ 1900 (tm:year t)) (+ 1 (tm:mon t))
                   (tm:mday t) (tm:hour t) (tm:min t) (tm:sec t))))))
         (offset
           (if (zero? offset) "Z"
             (apply
               (l (sign numbers)
                 (string-append sign (string-join (map number->padded-string numbers) ":")))
               (let* ((hms (drop-right (utc-duration->hms offset) 1)) (hours (first hms)))
                 (if (any negative? hms) (list "-" (map (l (a) (* -1 a)) hms)) (list "+" hms)))))))
       (string-append date-time offset)))

l: lambda, first: car

the code passes these tests (examples of valid strings):
https://github.com/sph-mn/sph-lib/blob/master/modules/test/module/sph/time/rfc3339.scm

for reference, the complete code: https://github.com/sph-mn/sph-lib/blob/master/modules/sph/time/rfc3339.scm

Re: How do you format date-times in RFC 3339 style?

[tantalum]

i once wrote a rfc3339 reader/writer and worked through some gotchas, 
maybe the code contains hints that are helpful.
for example, here is a function that converts from a timestamp to a 
rfc3339 date string:

   (define* (utc->rfc3339 a #:optional (offset 0) (seconds-fraction 0))
     "integer:posix-time -> string"
     (let
       ( (date-time
           (let (t (gmtime (+ a offset)))
             (apply
               (l (y m d h mi s)
                 (string-append y "-"
                   m "-"
                   d "T"
                   h ":"
                   mi ":"
                   s
                   (if (zero? seconds-fraction) ""
                     (string-append "." (number->string 
seconds-fraction)))))
               (map number->padded-string
                 (list (+ 1900 (tm:year t)) (+ 1 (tm:mon t))
                   (tm:mday t) (tm:hour t) (tm:min t) (tm:sec t))))))
         (offset
           (if (zero? offset) "Z"
             (apply
               (l (sign numbers)
                 (string-append sign (string-join (map 
number->padded-string numbers) ":")))
               (let* ((hms (drop-right (utc-duration->hms offset) 1)) 
(hours (first hms)))
                 (if (any negative? hms) (list "-" (map (l (a) (* -1 a)) 
hms)) (list "+" hms)))))))
       (string-append date-time offset)))

l: lambda, first: car

the code passes these tests (examples of valid strings):
https://github.com/sph-mn/sph-lib/blob/master/modules/test/module/sph/time/rfc3339.scm

for reference, the complete code: 
https://github.com/sph-mn/sph-lib/blob/master/modules/sph/time/rfc3339.scm

Re: How do you format date-times in RFC 3339 style?

[sirgazil]

Hi, tantalum.


El 12/02/19 a las 1:33 p. m., tantalum escribió:
> i once wrote a rfc3339 reader/writer and worked through some gotchas, 
> maybe the code contains hints that are helpful.
> for example, here is a function that converts from a timestamp to a 
> rfc3339 date string:
> 
>    (define* (utc->rfc3339 a #:optional (offset 0) (seconds-fraction 0))
>      "integer:posix-time -> string"
>      (let
>        ( (date-time
>            (let (t (gmtime (+ a offset)))
>              (apply
>                (l (y m d h mi s)
>                  (string-append y "-"
>                    m "-"
>                    d "T"
>                    h ":"
>                    mi ":"
>                    s
>                    (if (zero? seconds-fraction) ""
>                      (string-append "." (number->string 
> seconds-fraction)))))
>                (map number->padded-string
>                  (list (+ 1900 (tm:year t)) (+ 1 (tm:mon t))
>                    (tm:mday t) (tm:hour t) (tm:min t) (tm:sec t))))))
>          (offset
>            (if (zero? offset) "Z"
>              (apply
>                (l (sign numbers)
>                  (string-append sign (string-join (map 
> number->padded-string numbers) ":")))
>                (let* ((hms (drop-right (utc-duration->hms offset) 1)) 
> (hours (first hms)))
>                  (if (any negative? hms) (list "-" (map (l (a) (* -1 a)) 
> hms)) (list "+" hms)))))))
>        (string-append date-time offset)))
> 
> l: lambda, first: car
> 
> the code passes these tests (examples of valid strings):
> https://github.com/sph-mn/sph-lib/blob/master/modules/test/module/sph/time/rfc3339.scm 

 From these tests, I think this could work for me, thanks.


> for reference, the complete code: 
> https://github.com/sph-mn/sph-lib/blob/master/modules/sph/time/rfc3339.scm

You know what would be great? If you packaged "sph-lib" for GNU Guix :) 
That way I could easily install it and your library would be visible in 
the list of packages in Guile website.


-- 
Luis Felipe López Acevedo
http://sirgazil.bitbucket.io/

Re: How do you format date-times in RFC 3339 style?

[tantalum]

> You know what would be great? If you packaged "sph-lib" for GNU Guix

that is a good point, i plan on trying to do that, again. with the last 
two tries i couldnt find a simple example or documentation for creating 
a guix package that doesnt use autotools.

Re: How do you format date-times in RFC 3339 style?

[Ricardo Wurmus]

tantalum <sph@posteo.eu> writes:

>> You know what would be great? If you packaged "sph-lib" for GNU Guix
>
> that is a good point, i plan on trying to do that, again. with the
> last two tries i couldnt find a simple example or documentation for
> creating a guix package that doesnt use autotools.

You can use the guile-build-system.  You can look at
guile-picture-language in gnu/packages/guile-xyz.scm in the Guix sources
for an example.

-- 
Ricardo