Re: Lenses in Guile?

[Alex Sassmannshausen]

Heya,

Zelphir Kaltstahl <address@hidden> writes:

> Hi!
>
> This reminds me of something: Is there something like
> https://docs.racket-lang.org/lens/index.html for Guile? Or perhaps an
> easy to understand tutorial on implementing it?

Check out https://gitlab.com/a-sassmannshausen/guile-lens

It's an implementation I did for fun a while ago.  Can't remember how
faithfully it implements lenses as compared with racket's…

Best wishes,

Alex

>
> Regards,
> Zelphir
>
> On 2/18/20 2:38 PM, Christopher Lam wrote:
>> A bit late, and perhaps not as sophisticated as some bigger modules here.
>>
>> Two functions defined as follows: nested-alist-set! nested-alist-get at
>> https://github.com/Gnucash/gnucash/blob/1f83cfaf64d1cd3c8862b427dd043154f780a772/gnucash/report/html-chart.scm#L37
>>
>> Consider a nested alist describing unix file system
>> (define lst
>>  (list
>>   (cons 'usr (list
>>               (cons 'bin "binary files")
>>               (cons 'games "g4m3s")
>>               (cons 'include (list
>>                               (cons 'guile (list
>>                                             (cons '2.2 "old")))
>>                               (cons 'linux "da best")))))))
>>
>> We can access a leaf node via (nested-alist-get lst '(usr include linux))
>> --> "da best", and set a leaf node via (nested-alist-set! lst '(usr include
>> python) "boo"). This is probably easy to seasoned schemers, but still a
>> nice pair of functions to use in modifying nested alists before conversion
>> into json.
>>
>> On Mon, 17 Feb 2020 at 09:16, Ludovic Courtès <address@hidden> wrote:
>>
>>> Hi!
>>>
>>> Ricardo Wurmus <address@hidden> skribis:
>>>
>>>> What do you think about adding these things to
>>>> https://notabug.org/cwebber/guile-webutils/ ?  This was once intended to
>>>> be a collection of useful tools that come in handy when writing web
>>>> applications.
>>> I didn’t know about guile-webutils but consolidating Web tools in this
>>> package sounds like a great idea!
>>>
>>> Ludo’.
>>>
>>>