Besides the documentation procedure, this module exports two curry procedures, @> and @<, one macro, @@, and a sharp-read-macro, ##, which abbreviates the call of that latter macro. They all create partial procedures.
The macro transforms expressions with zero or more holes into a procedure. Insofar, it's a bit like cut or cute. But while in cut or cute a hole is the special identifier <>, in this module it's a pair of bangs, possibly enclosing a sequence of digits, for examples !! or !1!. In this way, holes needn't name different variables like in cut or cute.
Another difference to cut or cute is, that the holes may appear in nested expressions at different levels. This gives great flexibility. And the sharp-read-syntax ## adds ease of use.
The macro also provides an alternative syntax for anonymous procedures. ##(x y : xpr . xprs) abbreviates (lambda (x y) xpr . xprs)
shows the definition of the @@ macro.
@@[syntax] (@@ code)
extracts the holes out of the argument expression, code, sorts them numerically while removing dups and considers the resulting list as the argument list of a procedure, with code as body.
Alternatively, searches for a colon in code, checks if the expressions to the left of it are all symbols without dups, and considers those symbols as argument list of a procedure with body the expressions to the right of the colon.
This macro can be called with sharp-read-syntax ## as well. Note, that ##xpr is always a procedure, maybe a thunk, if there are no holes in xpr.
@>[procedure] (@> proc . head)
returns a curried procedure with arguments tail, which applies proc to (append head tail)
@<[procedure] (@< proc . tail)
returns a curried procedure with arguments head, which applies proc to (append head tail)
->proc[syntax] (->proc code)
alias to @@, deprecated
((@> map add1) '(0 1 2)) ; -> '(1 2 3) ((@< list-ref 2) '(0 1 2 3)) ; -> 2 ((@@ 5)) ; -> 5 (##5) ; -> 5 ##(vector 1 !!) ; -> procedure (call-with-values ##(values 1 2 3) list) ; -> '(1 2 3) (##(+ !1! 5) 2) ; -> 7 (##'(1 . 2)) ; -> '(1 . 2) (##(+ 5 (* !! 2)) 7) ; -> 19 (##(!! 1 2 3) *) ; -> 6 (##(!! 1 2 3) +) ; -> 6 (##(list 1 2 (vector 3 4 !! 6)) 5) ; -> '(1 2 #(3 4 5 6)) (##(list 1 2 #(3 4 !! 6))) ; note that the third arg of list is quoted ; hence there are no holes and we get a thunk ; -> '(1 2 #(3 4 !! 6))) (##(vector 1 2 !!) 3) ; -> #(1 2 3) (##(list 1 !! 2 !1!) 3 4) ; -> '(1 3 2 4) (##(list 1 !! 2 !!) 3) ; -> '(1 3 2 3) (##(list 1 !! 2 (vector !!)) 3) ; -> '(1 3 2 #(3)) ((##(lambda (x) (- x !!)) 2) 3) ; -> 1 (##(list !! !1! 2 (vector !!)) 1 2) ; -> '(1 2 2 #(1))) (##(cons !2! !1!) 1 2) ; -> '(2 . 1) (##(list (cons !2! !1!) (cons !1! !2!)) 1 2) ; -> '((2 . 1) (1 . 2)) (##(x y : (+ x y)) 1 2) ; -> 3
Feb 11, 2017
Copyright (c) 2016-2017, Juergen Lorenz All rights reserved.
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- ->proc renamed @@, curried procedures @> and @< added
- added alternative lambda syntax with a colon
- holes now numerically sorted
- bug with adjacent holes fixed, regexes replaced
- initial import