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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 53 |
1 files changed, 53 insertions, 0 deletions
@@ -43611,6 +43611,59 @@ place denotes a value stored in a dynamic data set such as a hash table, then deletion of that place implies deletion of the entry which holds that value. If the entry is identified by a key, that key is also removed. +If +.code place +is a DWIM bracket expression indexing into a structure, the structure +is expected to implement the +.code lambda +and +.code lambda-set +methods. Moreover, the place form must have only two arguments: +the object and an index argument. In other words, the +.code del +form must have this syntax: + +.mono +.mets (del >> [ obj << index ]) +.onom + +The +.code lambda +method will be invoked with the unmodified +.meta obj +and +.meta index +arguments to determine the prior value to be returned. +Then the +.code lambda-set +method will be invoked with three arguments: +.metn obj , +a possibly modified +.meta index +value and the argument +.code nil +representing an empty replacement sequence. + +If +.meta index +is a sequence or range, it is passed to the +.code lambda-set +method unmodified. Otherwise it is expected to be an integer, and +converted into a one-element range spanning the indicated element. +For instance, if the +.meta index +value is +.codn 3 , +it is converted to the range +.codn "#R(3 4)" . +In effect, the +.code lambda-set +method is thereby asked to replace the one-element subsequence starting at +index +.code 3 +with the empty sequence +.codn nil . + .coNP Macro @ lset .synb .mets (lset <> { place }+ << sequence-expr ) |