diff options
| -rw-r--r-- | lib.c | 14 | ||||
| -rw-r--r-- | txr.1 | 28 |
2 files changed, 34 insertions, 8 deletions
@@ -8160,9 +8160,19 @@ val alist_nremove1(val list, val key) return list; } -val copy_cons(val c) +val copy_cons(val cell) { - return cons(car(c), cdr(c)); + switch (type(cell)) { + case CONS: + case LCONS: + { + val obj = make_obj(); + *obj = *cell; + return obj; + } + default: + type_mismatch(lit("copy-cons: ~s is not a cons"), cell, nao); + } } val copy_alist(val list) @@ -19377,12 +19377,28 @@ for the empty list .desc The .code copy-cons -function creates a fresh cons cell, whose -.code car -and -.code cdr -fields are copied from -.codn cons . +function creates and returns a new object that is a replica of +.metn cons . + +The +.meta cons +argument must be either a +.code cons +cell, or else a lazy cons: an object of type +.codn lcons . + +A new cell of the same type as +.meta cons +is created, and all of its fields are initialized by +copying the corresponding fields from +.metn cons . + +If +.meta cons +is lazy, the newly created object is in the same +state as the original. If the original has not yet been updated +and thus has an update function, the copy also has not yet been +updated and has the same update function. .coNP Functions @ reverse and @ nreverse .synb |