Firstly many thanks for the explanation of the use of "literal-id" in macros.
As a simple exercise in learning how to use Racket macros, I'm trying to
simulate using C style array indices syntax in accessing nested Racket vectors.
I'm able to set up a macro to access a nexted Racket vector using a syntax
like: (array-ref v3[0 1 2] )
(define v #( #(1 2 3) #(11 22 33) #(111 222 333)))
(define v1 #( #(4 5 6) #(44 55 66) #(444 555 666)))
(define v3 (vector v v1))
(define-syntax array-ref
(syntax-rules ()
[(array-ref v [d1]) (vector-ref v d1)]
[(array-ref v [d1 d2 ... ]) (array-ref (vector-ref v d1) [d2 ... ])]))
I can set up a macro to access a two-dimensional vector with a syntax like
(array-ref1 v[0,1])
(define-syntax array-ref1
(syntax-rules ()
[(array-ref1 v [d1]) (vector-ref v d1)]
[(array-ref1 v [d1 , d2 ]) (array-ref1 (array-ref1 v [d1]) [ d2 ])]))
But when I do the following
(define-syntax array-ref1
(syntax-rules ()
[(array-ref1 v [d1]) (vector-ref v d1)]
[(array-ref1 v [d1 , d2 ]) (array-ref1 (array-ref1 v [d1]) [ d2 ])]
[(array-ref v [d1 , d2 , d3]) (array-ref (array-ref (array-ref v [d1])
[d2]) [d3])]))
I get this error:
syntax-rules: variable used twice in pattern in: unquote
Putting a comma as a literal-id doesn't help, it gives the error
Module Language: invalid module text
. read: unexpected `)'
Ideally I'd like to be able to set up a macro that can access any level of
nested vectors.
I.e. how do I show in the pattern that I want to repeat not just a pattern
variable but ", pattern variable".
Many thanks,
Harry Spier
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