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(guile.info)Sloppy Alist Functions

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Sloppy Alist Functions
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`sloppy-assq', `sloppy-assv' and `sloppy-assoc' behave like the
corresponding non-`sloppy-' procedures, except that they return `#f'
when the specified association list is not well-formed, where the
non-`sloppy-' versions would signal an error.

Specifically, there are two conditions for which the non-`sloppy-'
procedures signal an error, which the `sloppy-' procedures handle
instead by returning `#f'.  Firstly, if the specified alist as a whole
is not a proper list:

     (assoc "mary" '((1 . 2) ("key" . "door") . "open sesame"))
     =>
     ERROR: In procedure assoc in expression (assoc "mary" (quote #)):
     ERROR: Wrong type argument in position 2 (expecting NULLP): "open sesame"
     ABORT: (wrong-type-arg)
     
     (sloppy-assoc "mary" '((1 . 2) ("key" . "door") . "open sesame"))
     =>
     #f

Secondly, if one of the entries in the specified alist is not a pair:

     (assoc 2 '((1 . 1) 2 (3 . 9)))
     =>
     ERROR: In procedure assoc in expression (assoc 2 (quote #)):
     ERROR: Wrong type argument in position 2 (expecting CONSP): 2
     ABORT: (wrong-type-arg)
     
     (sloppy-assoc 2 '((1 . 1) 2 (3 . 9)))
     =>
     #f

Unless you are explicitly working with badly formed association lists,
it is much safer to use the non-`sloppy-' procedures, because they help
to highlight coding and data errors that the `sloppy-' versions would
silently cover up.

 - primitive: sloppy-assq key alist
     Behaves like `assq' but does not do any error checking.
     Recommended only for use in Guile internals.

 - primitive: sloppy-assv key alist
     Behaves like `assv' but does not do any error checking.
     Recommended only for use in Guile internals.

 - primitive: sloppy-assoc key alist
     Behaves like `assoc' but does not do any error checking.
     Recommended only for use in Guile internals.