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Re: pcase bindings in patterns with complicated logic
From: |
Thierry Volpiatto |
Subject: |
Re: pcase bindings in patterns with complicated logic |
Date: |
Sun, 14 Jan 2024 17:54:50 +0000 |
Ihor Radchenko <yantar92@posteo.net> writes:
> Thierry Volpiatto <thievol@posteo.net> writes:
>
>>>> [ BTW I don't understand why `app` pattern exists as long as now `pred` is
>>>> supporting an extra arg ]
>>>
>>> Isn't it explained right in the manual?
>>>
>>> ‘(app FUNCTION PATTERN)’
>>> Matches if FUNCTION called on EXPVAL returns a value that matches
>>> PATTERN. FUNCTION can take one of the forms described for ‘pred’,
>>> above. Unlike ‘pred’, however, ‘app’ tests the result against
>>> PATTERN, rather than against a boolean truth value.
>>
>> Perhaps it is right but I don't understand it, an example in the manual
>> would be welcome (if there is one I missed it).
>
> Does this example help?
>
> (pcase '(1 2 3)
> ((app cdr `(2 ,c)) (format "Match: %S" c)))
>
> You cannot easily do the same with pred.
Yes, thanks.
--
Thierry
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- pcase bindings in patterns with complicated logic, Richard Stallman, 2024/01/12
- Re: pcase bindings in patterns with complicated logic, Ihor Radchenko, 2024/01/13
- Re: pcase bindings in patterns with complicated logic, Thierry Volpiatto, 2024/01/14
- Re: pcase bindings in patterns with complicated logic, Thierry Volpiatto, 2024/01/14
- Re: pcase bindings in patterns with complicated logic, Ihor Radchenko, 2024/01/14
- Re: pcase bindings in patterns with complicated logic, Thierry Volpiatto, 2024/01/14
- Re: pcase bindings in patterns with complicated logic, Ihor Radchenko, 2024/01/14
- Re: pcase bindings in patterns with complicated logic,
Thierry Volpiatto <=
- Re: pcase bindings in patterns with complicated logic, Richard Stallman, 2024/01/15
- Re: pcase bindings in patterns with complicated logic, Ihor Radchenko, 2024/01/16
- Re: pcase bindings in patterns with complicated logic, Richard Stallman, 2024/01/17
- Re: pcase bindings in patterns with complicated logic, Ihor Radchenko, 2024/01/18
- Re: pcase bindings in patterns with complicated logic, Richard Stallman, 2024/01/19
- Re: pcase bindings in patterns with complicated logic, Ihor Radchenko, 2024/01/20
- Re: pcase bindings in patterns with complicated logic, Richard Stallman, 2024/01/20
- Re: pcase bindings in patterns with complicated logic, Ihor Radchenko, 2024/01/21
- Re: pcase bindings in patterns with complicated logic, Richard Stallman, 2024/01/23
- Re: pcase bindings in patterns with complicated logic, Stefan Monnier, 2024/01/23