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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 60 |
1 files changed, 60 insertions, 0 deletions
@@ -14191,6 +14191,66 @@ then .code nil is returned. +.coNP Accessor @ nthcdr +.synb +.mets (nthcdr < index << list ) +.mets (set (nthcdr < index << list ) << new-value ) +.syne +.desc +The +.code nthcdr +function retrieves the n-th cons cell of a list, indexed from zero. +The +.meta index +parameter must be a non-negative integer. If +.meta index +specifies a nonexistent cons beyond the end of the list, +then +.code nthcdr +yields nil. +The following equivalences hold: + +.cblk + (nthcdr 0 list) <--> list + (nthcdr 1 list) <--> (cdr list) + (nthcdr 2 list) <--> (cddr list) +.cble + +An +.code nthcdr +place designates the storage location which holds the n-th cell, +as indicated by the value of +.metn index . +Indices beyond the last cell of +.meta list +do not designate a valid place. +If +.meta list +is itself a place, then the zeroth index is permitted and the +resulting place denotes +.metn list . +Storing a value to +.cblk +.meti (nthcdr < 0 << list) +.cble +overwrites +.metn list . +Otherwise if +.meta list +isn't a syntactic place, then the zeroth index does not designate a valid +place; +.meta index +must have a positive value. A +.code nthcdr +place does not support deletion. + +.TP* "Dialect Note:" +In Common Lisp, +.code nthcdr +is only a function, not an accessor; +.code nthcdr +forms do not denote places. + .coNP Accessors @, caar @, cadr @, cdar @, cddr ... @ cdddddr .synb .mets (caar << object ) |