[LSR v2.18] "Ripped, torn staff-lines" does not compile

[Pierre Perol-Schneider]

Dear Squad,

The snippet hereunder :
http://lsr.dsi.unimi.it/LSR/Item?id=668
does not compile after v.2.18/v2.16 upgrades.
It was made by Mark Polesky for version 2.12.0

Terminal says :
.../all/ripped,-torn-staff-lines.ly:67:6: error: GUILE signaled an error
for the expression beginning here
#(define zigzagTearHeight (- (cdr y-ext) (car y-ext)))
.../all/ripped,-torn-staff-lines.ly:68:6: error: GUILE signaled an error
for the expression beginning here
#(define (deg2rad x) (* x (/ (* (atan 1) 4) 180)))
.../all/ripped,-torn-staff-lines.ly:70:6: error: GUILE signaled an error
for the expression beginning here
#(define zigzagTearWidth
.../all/ripped,-torn-staff-lines.ly:78:17: error: GUILE signaled an error
for the expression beginning here
#`(0 . ,zigzagTearWidth)
.../all/ripped,-torn-staff-lines.ly:130:14: error: wrong type for argument
1. Expecting pair of numbers, found #<unspecified>
zigzagTear = \zigzagTearCustom #zigzagDefaultYext
#zigzagDefaultSerrationCount
Missing body expression in ((define zigzagTearHeight (- (cdr y-ext) (car
y-ext)))).
Missing body expression in ((define (deg2rad x) (* x (/ (* (atan 1) 4)
180)))).
Missing body expression in ((define zigzagTearWidth (/ zigzagTearHeight
serrations (* (tan (/ (deg2rad zigzagTearAngle) 2)) 2)))).
Unbound variable: zigzagTearWidth
.../usr/share/lilypond/current/scm/parser-ly-from-scheme.scm:71:22: In
procedure reverse! in expression (ly:parse-string-expression clone
lily-string ...):
.../usr/share/lilypond/current/scm/parser-ly-from-scheme.scm:71:22: Wrong
type argument in position 1: ((-4 . 4) #<unspecified> . #f)

I didn't go deep into the code (it's pretty late now) but after a quick
look I suppose it could be simplified by using \scale.

Cheers,
Pierre