diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 163 |
1 files changed, 85 insertions, 78 deletions
@@ -35302,21 +35302,22 @@ would return for the same arguments, and the last element is what .code rsearch would return. -.coNP Functions @ ref and @ refset +.coNP Accessor @ ref .synb .mets (ref < sequence << index ) -.mets (refset < sequence < index << new-value ) +.mets (set (ref < sequence << index ) << new-value ) .syne .desc The .code ref -and -.code refset -functions perform array-like indexing into sequences, as well as -objects of type -.code buf -and -.codn carray . +accessor performs array-like indexing into sequences, as well as +hash tables and objects of type +.codn buf , +.codn carray , +.code tree +as well as structure objects which define a +.code lambda +method. If the .meta sequence @@ -35346,41 +35347,6 @@ treats it as a list, traversing the structure using operations. In the absence of support for these operations, the function fails with an error exception. -Similarly, a structure supports -.code refset -directly if it has a -.code lambda-set -method. This gets called with -.meta index -and -.meta new-value -as arguments. Then -.meta new-value -is returned. -If a structure lacks a -.code lambda-set -method, then -.code refset -treats it as a list, traversing the structure using -.cod3 car / cdr -operations, and storing -.meta new-value -using -.codn rplaca . -In the absence of support for these operations, -the function fails with an error exception. - -The -.code ref -function retrieves an element of -.metn sequence , -whereas -.code refset -overwrites an -element of -.meta sequence -with a new value. - If .meta sequence is a sequence then @@ -35412,51 +35378,92 @@ is a search tree, then .code ref behaves like .codn tree-lookup . -The -.code refset -function is not supported by search trees. -The +A +.code ref +expression may be used as a place. Storing a value into a +.code ref +place is performed using the .code refset -function is strict for out-of-range indices over all sequences, -including lists. In the case of hashes, a +function. + +When the +.code del +operator is used to delete an index value from a +.code ref +place, the +.meta sequence +itself must be a place. The deletion calculates a new +sequence with the item at +.meta index +deleted; that new sequence is stored back into the +.meta sequence +place. Deletion does not use .code refset -of a nonexistent key creates the key. +but rather the +.code replace +function. +.coNP Function @ refset +.synb +.mets (refset < sequence < index << new-value ) +.syne +.desc The .code refset -function returns -.codn new-value . - -The following equivalences hold between -.code ref -and -.codn refset , -and the DWIM bracket syntax, provided that -.meta idx -is a scalar index and +function performs indexing into .meta sequence -is a sequence object, rather than a hash. - -.verb - (ref seq idx) <--> [seq idx] +in a manner identical to +.code ref +with the purpose of overwriting the indexed element with +.metn new-value . +It is a companion function to +.code ref +which is used in the implementation of the +.code ref +place. - (refset seq idx new) <--> (set [seq idx] new) -.brev +The return value of +.code ref-set +is +.metn new-value . -The difference is that -.code ref -and +If +.meta sequence +is a structure, it supports .code refset -are first class functions which -can be used in functional programming as higher order functions, whereas the -bracket notation is syntactic sugar, and -.code set -is an operator, not a function. -Therefore the brackets cannot replace all uses of -.code ref +directly if it has a +.code lambda-set +method. This gets called with +.meta index and -.codn refset . +.meta new-value +as arguments. Then +.meta new-value +is returned. +If a structure lacks a +.code lambda-set +method, then +.code refset +treats it as a list, traversing the structure using +.cod3 car / cdr +operations, and storing +.meta new-value +using +.codn rplaca . +In the absence of support for these operations, +the function fails with an error exception. + +The +.code refset +function is not supported by search trees. + +The +.code refset +function is strict for out-of-range indices over all sequences, +including lists. In the case of hashes, a +.code refset +of a nonexistent key creates the key. .coNP Function @ update .synb |