Question

Can a macro be written in Scheme (with define-syntax, for example) which will take expressions like this:

(op a b c d e f g h i j) 

And yield expressions like this as output?

(op (op (op (op (op (op (op (op (op a b) c) d) e) f) g) h) i) j)  

Of course, for arbitrary lengths. I can’t think of a way to do it, given some template like this:

(define-syntax op   (syntax-rules ()     [(_) 'base-case]     [(v1 v2 ...) 'nested-case??])) 

Answer 1

(define bop list)  (define-syntax op   (syntax-rules ()     ((op a b) (bop a b))     ((op a b c ...) (op (bop a b) c ...)))) 

For example, (op 1 2 3 4) expands to (bop (bop (bop 1 2) 3) 4) and evaluates to (((1 2) 3) 4).