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| -rw-r--r-- | txr.1 | 55 |
1 files changed, 55 insertions, 0 deletions
@@ -53830,6 +53830,60 @@ from a quasiliteral within a nested (op ... (op ... `@@@1`)) .brev +Because the +.code do +macro may be applied to operators, it is possible to apply it to itself, +as well as to +.codn op , +as in the following example: + +.verb + [[[[(do do do op list) 1] 2] 3] 4] -> (1 2 3 4) +.brev + +The chained application associates right-to-left: the rightmost +.code do +is applied to +.codn op ; +the second rightmost +.code do +is applied to the rightmost on and so on. The effect is that partial +application has been achieved. The value +.code 1 +is passed to the resulting function, which returns another function +which takes the next argument. Finally, all these chained argument +values are passed to +.codn list . + +Each +.cod3 do / op +level is processed independently. The following examples show how the list may +be permuted into several different orders by referring to an implicit argument +at various levels of nesting, making it the first argument of +.codn list . +The unmentioned arguments implicitly follow, in order. This works because +mentioning the argument explicitly means that its corresponding +.code do +operator no longer inserts its argument implicitly into body of the +function which it generates: + +.verb + [[[[(do do do op list @1) 1] 2] 3] 4] -> (4 1 2 3) + [[[[(do do do op list @@1) 1] 2] 3] 4] ->(3 1 2 4) + [[[[(do do do op list @@@1) 1] 2] 3] 4] -> (2 1 3 4) + [[[[(do do do op list @@@@1) 1] 2] 3] 4] -> (1 2 3 4)) +.brev + +The following example mentions all arguments at every +.cod3 do / op +nesting level, thereby explicitly establishing the order +in which they are passed to +.codn list : + +.verb + [[[[(do do do op list @1 @@1 @@@1 @@@@1) 1] 2] 3] 4] -> (4 3 2 1) +.brev + .TP* Examples: .verb @@ -53839,6 +53893,7 @@ from a quasiliteral within a nested (reduce-left (op + (* 10 @1) @2) '(1 2 3)) --> 123 .brev + .coNP Macro @ lop .synb .mets (lop << form +) |