diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 87 |
1 files changed, 80 insertions, 7 deletions
@@ -32073,6 +32073,13 @@ iterative or recursive process can be collected easily using .code list-builder in the order they are visited. +The +.code list-builder +type provides methods for adding and removing items at either end of +the list, making it suitable where a +.I dequeue +structure is required. + The basic workflow begins with the instantiation of a .code list-builder object. This object may be initialized with a piece of list material which @@ -32320,22 +32327,57 @@ into the construction methods on the same object. -> (1 2 1 2 1 2 1 2) .brev -.coNP Macro @ build +.coNP Methods @ del and @ del* +.synb +.mets << list-builder .(del) +.mets << list-builder .(del*) +.syne +.desc +The +.code del +and +.code del* +methods each remove an element from the list and return it. +If the list is empty, they return +.codn nil . + +The +.code del +method removes an element from the front of the list, whereas +.code del* +removes an element from the end of the list. + +Note: this orientation is opposite to +.code add +and +.codn add* . +Thus +.code del +pairs with +.code add +to produce FIFO queuing behavior. + +.coNP Macros @ build and @ buildn .synb .mets (build << form *) +.mets (buildn << form *) .syne .desc The .code build -macro provides a shorthand notation for constructing lists using the +and +.code buildn +macros provide a shorthand notation for constructing lists using the .code list-builder -structure. It eliminates the explicit call to the +structure. They eliminate the explicit call to the .code build-list -function to construct the object, and eliminates the explicit +function to construct the object, and eliminate the explicit references to the object. Instead, .code build +and +.code buildn creates a lexical environment in which a .code list-builder object is implicitly constructed and bound to a hidden variable. @@ -32344,14 +32386,45 @@ Local functions which mimic the methods operate implicitly on this hidden variable, so that the object need not be mentioned as an argument. +Then, each +.meta form +is evaluated in order. + +When the last +.meta form +is evaluated, +.code build +returns the constructed list, whereas +.code buildn +returns the value of the last +.metn form . + +If no forms are enclosed, both macros return +.codn nil . + With the exception of .codn get , -these local functions -.codn get , -have unspecified return values, like the same-named +the local functions have unspecified return values, like the same-named .code list-builder methods. +Note: because the local function +.code del +has the same name as a global macro, it is implemented as a +.code macrolet. +Inside a +.code build +or +.codn buildn , +if +.code del +is invoked with no arguments, then it denotes a call to the +.code list-builder +.code del +method. If invoked with an argument, then it resolves to the global +.code del +macro for deleting a place. + .TP* Examples: .verb |