FWIW, I like to assert that the familiar "FOR A = 1 TO 10" is actually
not often needed in idiomatic Scheme. More often, you're processing a
sequence, or you're doing functional programming such that you need to
recurse anyway to avoid mutation, or you need premature exits
sometimes. One possible exception that comes to mind is if you're
writing a matrix math library, but in that case you might make your own
procedures or syntax for iterating/folding over matrices in different ways.
Anyway, for the benefit of anyone new to syntax extensions, here is a
syntax definition that supports the "for-loop" example (warning: it
doesn't error-check as much as it should, because that would clutter the
example). You can paste this into DrRacket and use the Macro Stepper to
watch how it expands.
((_ (VAR START END) BODY0 BODY1 ...)
(let ((end-val END))
(let loop ((VAR START))
(if (> VAR end-val)
(begin BODY0 BODY1 ...
(loop (add1 VAR)))))))))
(for-loop (i 1 10) (print i))
(for/list ([i (in-range 1 10)]) i)
'(1 2 3 4 5 6 7 8 9)
All about for loops: http://docs.racket-lang.org/guide/for.html