Clearing the contents of a dictionary

[Yegappan Lakshmanan]

Hi,

To clear the contents of a list named "abc", we can use "unlet abc[:]".

It looks like a similar method for clearing the contents of a dictionary

is not available. We can set the dictionary variable to another empty

dictionary (but it is not the same). Am I missing something?

Thanks,

Yegappan

[Tony Mechelynck]

You mean, after :let xyz = {} the old keys and values still exist? I
wouldn't have expected that.

Oh, and what about
for k in keys(xyz) | exe 'unlet xyz.' .. k | endfor
?

Best regads,
Tony.

[Yegappan Lakshmanan]

Hi Tony,

On Sun, May 24, 2020 at 5:44 PM Tony Mechelynck <antoine.m...@gmail.com> wrote:

On Mon, May 25, 2020 at 2:15 AM Yegappan Lakshmanan <yega...@gmail.com> wrote:
>
> Hi,
>
> To clear the contents of a list named "abc", we can use "unlet abc[:]".
> It looks like a similar method for clearing the contents of a dictionary
> is not available. We can set the dictionary variable to another empty
> dictionary (but it is not the same). Am I missing something?
>
> Thanks,
> Yegappan

You mean, after :let xyz = {} the old keys and values still exist? I
wouldn't have expected that.

Consider the following function for clearing a List:

func ClearList(l)
    unlet a:l[:]
endfunc

let l = [1, 2, 3, 4]
call ClearList(l)
echo "List = ->" .. string(l) .. "<-"

After calling the ClearList() function, all the elements in the List

are cleared.

A similar function for clearing a Dict:

func ClearDict(d)
    for k in keys(a:d)
             unlet a:d[k]
    endfor
endfunc

let d = {'a' : 10, 'b' : 20}
call ClearDict(d)
echo "Dict = ->" .. string(d) .. "<-"

In this function, we have to iterate through all the keys and unlet each

item. The Dict cannot be cleared by simply using unlet or by assigning

the argument to an empty dictionary.

 

Regards,

Yegappan

[Pavol Juhas]

How about filter(d, “0”) ?
To my understanding it clears the dictionary in place.

[Yegappan Lakshmanan]

Hi,

On Sun, May 24, 2020 at 8:37 PM Pavol Juhas <pavol...@gmail.com> wrote:

How about  filter(d, “0”) ?
To my understanding it clears the dictionary in place.

Yes. Good idea. This does clear all the items in the dict. But for consistency

reasons, it will be useful to have unlet also support clearing all the items

in a Dict.

Thanks,

Yegappan

[Bram Moolenaar]

The "unlet" command would be a weird way to clear a dict.
The suggestion to use filter() works well enough:

call filter(dict, 0)

Adding a new function isn't really needed, I would think clearing a
dictionary while keeping the identity is rare.

--
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... You'd have to press the "Start" button to turn the engine off.

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[Andy Wokula]

Am 25.05.2020 um 22:35 schrieb Bram Moolenaar:
> Yegappan wrote:
>
>> To clear the contents of a list named "abc", we can use "unlet abc[:]".
>> It looks like a similar method for clearing the contents of a dictionary
>> is not available. We can set the dictionary variable to another empty
>> dictionary (but it is not the same). Am I missing something?
>
> The "unlet" command would be a weird way to clear a dict.
> The suggestion to use filter() works well enough:
>
> call filter(dict, 0)
>
> Adding a new function isn't really needed, I would think clearing a
> dictionary while keeping the identity is rare.

:h filter()
already mentions this method.

But for 0, a string should be used, similar to searchpair()'s {skip} expression
(which does not accept a number):
:call filter(dict, "0")

--
Andy