[CM] About the implementation of sturms function in Notes from the Metalevel

Fri, 28 Oct 2005 22:41:13 +0300

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I came to the 12. Chapter of Notes from the Metalevel
book and while I was trying to compile the sturms function
I had some warning from SBCL:

The details are at:

http://paste.lisp.org/display/12980

;; the code below (which is taken from Common Music
;; application produces an error:
;;
;;-+  Warnings (1)
;; `-- =3D=3D>
;;       -1
;;     This is not a (OR (SINGLE-FLOAT (0.0)) (DOUBLE-FLOAT (0.0d0)) =
(RATIONAL (0))):
;;       -1
;;     See also:
;;       SBCL Manual, Handling of Types [node]

(define (strums key1 key2 rate dur amp)
  (let ((step (if (< key2 key1) -1 1)) ;; e.g. 1 2 gives no warn.
        (diff (abs (- key1 key2))))
    (loop repeat (+ diff 1)
          for key from key1 by step
          for beg from 0 by rate
          collect (new midi
                    :time beg
                    :duration dur
                    :amplitude amp
                    :keynum key))))

One of the possible solutions was to use a slightly different for in
the loop:

; this seems to solve the problem of
;; a potential *negative* stepping value

(define (strums key1 key2 rate dur amp)
  (let ((step (if (< key2 key1) -1 1))
        (diff (abs (- key1 key2))))
    (loop repeat (+ diff 1)
          for key =3D key1 then (+ key step)
          for beg from 0 by rate
          collect (new midi
                    :time beg
                    :duration dur
                    :amplitude amp
                    :keynum key))))

Another proposed solution is to to do a conditional rotatef of key1 and =
key2=20
and then do a for key from key1 to key2.

PS: Maybe this is already corrected in the CD that came with the
book (I couldn't find scores.cm in CVS version of CM) but I'm just the =
type of=20
guy who likes to type code from the book and I just wanted to share this
just in case somebody else is stuck in the same place.

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I came to the 12. Chapter of Notes from the =
Metalevel 
book and while I was trying to compile the sturms function 
I had some warning from SBCL: 
 
The details are at: 
 
<A =
HREF=3D"http://paste.lisp.org/display/12980">http://paste.lisp.org/displa=
y/12980</A> 
 
;; the code below (which is taken from Common Music 
;; application produces an error: 
;; 
;;-+&nbsp; Warnings (1) 
;; `-- =3D=3D&gt; 
;;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; -1 
;;&nbsp;&nbsp;&nbsp;&nbsp; This is not a (OR (SINGLE-FLOAT (0.0)) =
(DOUBLE-FLOAT (0.0d0)) (RATIONAL (0))): 
;;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; -1 
;;&nbsp;&nbsp;&nbsp;&nbsp; See also: 
;;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; SBCL Manual, Handling of Types =
[node] 
 
 
(define (strums key1 key2 rate dur amp) 
&nbsp; (let ((step (if (&lt; key2 key1) -1 1)) ;; e.g. 1 2 gives no =
warn. 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (diff (abs (- key1 =
key2)))) 
&nbsp;&nbsp;&nbsp; (loop repeat (+ diff 1) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; for key from key1 =
by step 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; for beg from 0 by =
rate 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; collect (new =
midi 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :time beg 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :duration dur 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :amplitude amp 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :keynum key)))) 
 
 
 
One of the possible solutions was to use a slightly different for in 
the loop: 
 
 
; this seems to solve the problem of 
;; a potential *negative* stepping value 
 
(define (strums key1 key2 rate dur amp) 
&nbsp; (let ((step (if (&lt; key2 key1) -1 1)) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (diff (abs (- key1 =
key2)))) 
&nbsp;&nbsp;&nbsp; (loop repeat (+ diff 1) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; for key =3D key1 =
then (+ key step) 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; for beg from 0 by =
rate 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; collect (new =
midi 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :time beg 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :duration dur 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :amplitude amp 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :keynum key)))) 
 
Another proposed solution is to to do a conditional rotatef of key1 and =
key2 
and then do a for key from key1 to key2. 
 
PS: Maybe this is already corrected in the CD that came with the 
book (I couldn't find scores.cm in CVS version of CM) but I'm just the =
type of 
guy who likes to type code from the book and I just wanted to share =
this 
just in case somebody else is stuck in the same place.

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