[gambit-list] Invalid Syntax after loading syntax-case

Joel J. Adamson jadamson at partners.org
Mon Feb 4 13:52:26 EST 2008


Dear List,

I have the following procedure that takes a list of vectors or a list of
lists and flattens the list to create a structure called `f64matrix'.  

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
;;this can be a list of lists, list of vectors, or a flat list
;; it would be better to only write out this error once, instead of three times
(define (list->f64matrix lst #!optional rows cols)
  (letrec ((rows->f64matrix
	    ;; this procedure delegates in the uncertain case of
	    ;; (list->f64matrix lst #f #f)
	    (lambda (lst)
	      ;; is the list a list of lists?
	      (cond ((list? (car lst))
		     (lol->f64matrix lst))
		    ;; or is it a list of vectors?
		    ((f64vector? (car lst))
		     (lov->f64matrix lst))
		    ;; otherwise it is one row
		    (else (lst->f64matrix lst 1 (length lst))))))
	   (lst->f64matrix
	    ;; this procedure actually makes the matrix given n rows
	    ;; and m columns and a list
	    (lambda (lst rows cols)
	      (if (= (* rows cols) (length lst))
		  (make-f64matrix rows cols (list->f64vector lst))
		  (error "Not enough elements for given dimensions"))))
	   (lol->f64matrix
	    ;; this procedure takes a list of n lists of length m and
	    ;; passes a flattened version of lol to (lst->f64matrix
	    ;; lol n m)
	    (lambda (lol)
	      (let ((rows (length lol))
		    (cols (length (list-ref lol 0)))
		    (flatlol (flatten lol)))
		(if (= (* rows cols) (length flatlol))
		    ;; flatten the list
		    (lst->f64matrix flatlol rows cols)
		    (error "Not enough elements for given dimensions")))))
	   (lov->f64matrix
	    ;; This procedure transforms a list of n f64vectors of
	    ;; length m into a list and passes it to lst->f64matrix
	    ;; with n rows and m columns
	    (lambda (lov)
	      (let ((rows (length lov))
		    (cols (f64vector-length (list-ref lov 0)))
		    (flatlov (f64lov-flatten lov)))
		(if (= (* rows cols) (f64vector-length flatlov))
		    ;; flatten the vectors into one vector or list
		    (lst->f64matrix flatlov rows cols)
		    (error "Not enough elements for given dimensions"))))))
    ;; execution starts here:
    ;;
    ;; gatekeeper: if rows and columns is #f
    ;; then send to the delegating procedure rows->f64matrix, whose
    ;; default function is to set a flat list to the data element of a
    ;; matrix with one row
    (cond ((and rows cols)
	   ;; lst->f64matrix only takes lists because if you need to
	   ;; specify rows and columns and your input is a vector, you
	   ;; should just use make-f64matrix
	   (lst->f64matrix lst rows cols))
	  (else (rows->f64matrix lst)))))
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

This requires `flatten', defined by

;;;;;;;;;;;;;;;;;;;;list.ss;;;;;;;;;;;;;;;;;;;;
;; -*-mode:scheme-*-
;; list operations

;; flatten
;; this macro works on lists, however I encounter some funny behavior
;; since macros don't evaluate their arguments
;;(define-syntax flatten
;;   (syntax-rules ()
;;     ;; base case to stop recursion
;;     ((flatten (l1 l2 ...)) (list l1 l2 ...))
;;     ((flatten (l1 l2 ...) l3 ...)
;;      (append (list l1 l2 ...) (flatten l3 ...)))))

(define (flatten lol)
  (cond ((null? lol) '())
	((not (pair? lol)) lol)
	(else (append (car lol)
		      (flatten (cdr lol))))))

;; vector-list-flatten
(define (f64lov-flatten lov)
  (cond ((null? lov) '())
	((not (pair? lov)) (f64vector->list lov))
	((not (f64vector? (car lov))) (error "f64vector expected"))
	(else (append (f64vector->list (car lov))
		      (f64lov-flatten (cdr lov))))))
	 
;;end list.ss

Here's the problem: this (list->f64matrix) compiles just fine when I
define `flatten' as a function (flatten works just fine as a function,
but I need to work on macros, so I decided to try it as a macro).
However, if I copy ~~/syntax-case.scm to gambcext.scm and then compile,
I get an "invalid syntax" error during compilation.

What changes when I load "~~/syntax-case"?  Does the definition of
letrec change?

I appreciate any comments on the code, as well.

Thanks!
Joel


-- 
Joel J. Adamson
Biostatistician
Pediatric Psychopharmacology Research Unit
Massachusetts General Hospital
Boston, MA  02114
(617) 643-1432
(303) 880-3109

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