Prisms and Antiprisms

TO prism :n :r :h
  ; Generates an n-gonal prism of radius r and height h
  MAKE "s 2 * :r * SIN( 180 / :n ) ; Side length
  RU 90 FD :h / 2 RD 90 polygon :n :r
  RD 90 FD :h     RU 90 polygon :n :r
  FD :r RT 90 + 180 / :n
  PD RU 90 FD :h RD 90
  REPEAT :n [ FD :s RD 90 FD :h RU 180 FD :h RD 90 RT 360 / :n ] PU
  RT 90 - 180 / :n FD :r RT 180 RD 90 FD :h / 2 RU 90
END

TO antiprism :n :r :h
  RU 90 FD :h / 2 RD 90             polygon :n :r
  RD 90 FD :h     RU 90 RT 180 / :n polygon :n :r PU
  RT 90 FD :r RT 90
  RT 90 / :n PD
  FOR [ i 1 :n 1 ][
    MAKE "angle1 ( 360 * :i ) / :n
    MAKE "angle2 ( 360 * :i + 180 ) / :n
    MAKE "x1 :r * COS :angle1
    MAKE "x2 :r * COS :angle2  
    MAKE "z1 :r * SIN :angle1
    MAKE "z2 :r * SIN :angle2
    MAKE "diag SQRT ( :h ^ 2 + ( :x2 - x1 ) ^ 2 + ( :z2 - :z1 ) ^ 2 ) ; Triangle side length
    LOOKATXYZ( :x1 ) (  :h / 2 ) ( :z1 ) FD :diag
    LOOKATXYZ( :x2 ) ( -:h / 2 ) ( :z2 ) FD :diag
  ]
END