Node:Sloppy Alist Functions, Next:Alist Example, Previous:Removing Alist Entries, Up:Association Lists
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.
| sloppy-assq key alist | Scheme Procedure |
| scm_sloppy_assq (key, alist) | C Function |
Behaves like assq but does not do any error checking.
Recommended only for use in Guile internals.
|
| sloppy-assv key alist | Scheme Procedure |
| scm_sloppy_assv (key, alist) | C Function |
Behaves like assv but does not do any error checking.
Recommended only for use in Guile internals.
|
| sloppy-assoc key alist | Scheme Procedure |
| scm_sloppy_assoc (key, alist) | C Function |
Behaves like assoc but does not do any error checking.
Recommended only for use in Guile internals.
|