Changeset 37988 in project

Timestamp:

11/11/19 13:58:11 (8 months ago)

Author:

juergen

Message:

holes 1.2 with new delimiters and without read macros

File:

• wiki/eggref/5/holes (modified) (6 diffs)

wiki/eggref/5/holes

@@ -8 +8 @@
 
 Besides the documentation procedure, this module exports two curry
-procedures, @> and @<, one macro, @@, and a sharp-read-macro, ##, as
-well as a read-macro, ^, which abbreviates the call of that latter
-macro. They all create partial procedures.
+procedures, @> and @<, and one macro, @@, which implements the holes
+mechanism.
+They all create partial procedures.
 
-Holes are spezial identifiers, enclosing zero or more digits either by <
-and >, the new way, or by bangs !!, the old way.  You can choose between
-the two versions with a parameter named hole-delimiters.
+Holes are spezial identifiers, delimited by < and >, possibly enclosing
+zero or more digits. This new syntax replaces the old one, where both
+delimiters were bangs.
 
 The macro @@ transforms expressions with zero or more holes into a
 procedure which has as many arguments as there are different holes in
 the expression. Moreover, the arguments are ordered according to the
-digits enclosed by the delimiters.
-
-For example, (@@ 5), ##5 or ^5, which are all the same, is a thunk,
-because there are no holes. And ^(- <2> <1> <2>) is a procedure of two
+digits enclosed by the delimiters.  For example, (@@ 5), is a thunk,
+because there are no holes. And (@@ (- <2> <1> <2>)) is a procedure of two
 arguments, <1> and <2> in this order, returning (- 20 10 20) when
-applied to 10 20: (^(- <2> <1> <2>) 10 20) is -10.
+applied to 10 20: ((@@(- <2> <1> <2>)) 10 20) is -10.
 
 But holes aren't restricted to flat list expressions, nested ones are
-accepted as well. For example, ^(+ 5 (* <> 2)) is a unary procedure
+accepted as well. For example, (@@ (+ 5 (* <> 2))) is a unary procedure
 which applied to 7 gives 19. The holes may appear in different
 nesting levels, which gives great flexibility.
 
-Notice the difference of @@ to cut and cute, where two pairs <> <> accept
-different arguments, @@ would accept only one.
+Notice the difference of @@ to cut and cute. In the latter each pair
+<> accepts different arguments, whereas in the former different holes
+are needed.
 
 === Documentation
@@ -43 +42 @@
 the documentation of sym.
 
-==== hole-delimiters
-
-<parameter>(hole-delimiters [str])</parameter>
-
-returns or sets the hole-delimiters to either "<>", the default, or
-"!!".
-
 ==== @@
 
@@ -58 +50 @@
 argument list of a procedure, with code as body.
 
-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.
+Note, that (@@ xpr) is always a procedure, maybe a thunk, if there are no
+holes in xpr.
 
 ==== @>
@@ -84 +75 @@
 ((@> 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
+
+(((@@ (lambda (x) (- x <>))) 2) 3) ; ->1
+
+(call-with-values
+  (@@ (values 1 2 3))
+  list)
+  ;-> '(1 2 3)
+
+((@@ (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
+; -> '(1 2 #(3 4 <> 6))
+
+((@@ (list (cons <2> <1>) (cons <1> <2>))) 1 2)
+; -> '((2 . 1) (1 . 2))
 </enscript>
 
@@ -123 +103 @@
 == Last update
 
-Nov 07, 2019
+Nov 11, 2019
 
 == Author
@@ -161 +141 @@
 
 == Version History
+; 1.2 : parameter hole-delimiters and read macros removed,
+        only delimiters < and > accepted instead of bangs
 ; 1.1 : parameter hole-delimiters added accepting "<>" or "!!"
 ; 1.0 : port from chicken-4, version 1.4,  with modifications