fun error s = 
    (Page.return ("Error: " ^ s)
     `An error occurred while generating a recipe for 
      you; use your browser's back-button to backup 
      and enter a number in the form.`
     ; Web.exit())

  val persons = 
    case FormVar.wrapOpt FormVar.getNatErr "persons"
      of SOME n => real n
       | NONE => error "You must type a number"

  fun pr_num s r = 
    if Real.== (r,1.0) then "one " ^ s
    else 
      if Real.==(real(round r),r) then 
	Int.toString (round r) ^ " " ^ s ^ "s"
      else Real.toString r ^ " " ^ s ^ "s"

  val _ = Page.return "Apple Pie Recipe"
    `To make an Apple pie for ^(pr_num "person" persons), you 
     need the following ingredients:
     <ul> 
      <img align=right src=applepie.jpg>
      <li> ^(pr_num "cup" (persons / 16.0)) butter
      <li> ^(pr_num "cup" (persons / 4.0)) sugar
      <li> ^(pr_num "egg" (persons / 4.0))
      <li> ^(pr_num "teaspoon" (persons / 16.0)) salt
      <li> ^(pr_num "teaspoon" (persons / 4.0)) cinnamon
      <li> ^(pr_num "teaspoon" (persons / 4.0)) baking soda
      <li> ^(pr_num "cup" (persons / 4.0)) flour
      <li> ^(pr_num "cup" (2.5 * persons / 4.0)) diced apples
      <li> ^(pr_num "teaspoon" (persons / 4.0)) vanilla
      <li> ^(pr_num "tablespoon" (persons / 2.0)) hot water
     </ul>

     Combine ingredients in order given. Bake in greased 9-inch 
     pie pans for 45 minutes at 350F. Serve warm with whipped 
     cream or ice cream. <p>

     Make <a href=recipe.html>another recipe</a>.`