GNU bug report logs - #30237
Generalizing ‘and=>’

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From: Mathieu Lirzin <mthl <at> gnu.org>
To: 30237 <at> debbugs.gnu.org
Subject: bug#30237: Generalizing ‘and=>’
Date: Wed, 24 Jan 2018 13:10:20 +0100

Hello,

Here is a proposal for generalizing ‘and=>’ to a pipeline of procedures.
It acts like a “bind” operator in an ad-hoc “Maybe” monad which uses #f
to represent the absence of value.  Not sure if it is useful in
practice, but it feels like a natural generalization.

The current definition is the following:

  (define (and=> value procedure)
    (and value (procedure value)))

Here is my proposition:

  (define-syntax and=>
    (syntax-rules ()
      ((_) #t)
      ((_ val) val)
      ((_ val proc)
       (and val (proc val)))
      ((_ val proc proc* ...)
       (and=> (and val (proc val)) proc* ...))))

Let me know if such change is welcome or not, so I can provide a
complete patch including documentation.  Even if it's a small change, I
would like to assign copyright for future changes.

Thanks.

-- 
Mathieu Lirzin
GPG: F2A3 8D7E EB2B 6640 5761  070D 0ADE E100 9460 4D37

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