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Text File  |  1992-07-29  |  614 b   |  21 lines
  1.  
  2. (*********************************************************************
  3.  
  4.         Adapted from
  5.         Roman E. Maeder: Programming in Mathematica,
  6.         Second Edition, Addison-Wesley, 1991.
  7.  
  8.  *********************************************************************)
  9.  
  10.  
  11. GetNumber[prompt_String, predicate_:(True&)] :=
  12.     Module[{answer},
  13.         While[ True,
  14.             answer = Input[prompt];
  15.             If[ NumberQ[answer] && predicate[answer], Break[] ];  (* good   *)
  16.             If[ answer === EndOfFile, Break[] ];                  (* escape *)
  17.             Print["Please enter a number that satisfies ", predicate]
  18.         ];
  19.         answer
  20.     ]
  21.