% diamond.m4
.PS
# See LaTeX Graphics Companion pp 57-58
dimen = 1.5
ratio = 0.9
n = 30

North: (0,dimen)
East: (dimen,0)
South: (0,-dimen)
West: (-dimen,0)

define(`diamond',`
  ifdef(`pstricks_',
    `\pscustom[linecolor=white,linewidth=0pt,fillstyle=solid,fillcolor=`$1']{',
    `shade(ifelse(`$1',white,0,1),')
  line from North to East then to South then to West then to North
  ifdef(`pstricks_',`\relax}',`)')
 ')

for i = 2 to n do { 
  if (i % 2) == 0 then { diamond(black) } else { diamond(white) }
  Tmp: North
  North: ratio between East and North
  East: ratio between South and East
  South: ratio between West and South
  West: ratio between Tmp and West
  }
.PE