#Another exercise page 4 et 5
#idem but with out prefix notation => infix

Set $2Pi 6.28318530717959
Set $Factor ( 400 / $2Pi )
  Path {
    Width 1
    Move 100 400
    For $x0 0 200 {
      Set $x ( ( $2Pi / 200 ) * $x0 )
      Set $y Sin $x
      Set $t ( ( $x * $Factor ) + 100 )
      Set $u ( ( $y * $Factor ) + 400 )
      Line $t $u
    }
    Line 500 400
  }
  
Path {
    Width 0	# this means: as thin as possible
    Move 100 400
    Line 500 400
    Move 100   ( 400 - $Factor )
    Line 100   ( 400 + $Factor )
    # every pi/4 units:
    For $n 0 9 {
      Set $x ( ( $2Pi / 8 ) * $n )
      Set $t ( ( $x * $Factor ) + 100 ) 
      Move $t 390
      Line $t 410
    }
  }
