[Caml-list] out-of-bound array or string access

[Johann Spies <jspies@maties.sun.ac.za>]

When I run this small  program I get the following results:
------------------------
$ ./paaiement 10000 13.5 5

Die paaiement is R230.10
--------------------------
All arguments correct.  Result as expected...

--------------------------
$ ./paaiement 10000 -13.5 5
Die rentekoers (-13.500000) moet tussen 0 en 100.0 wees
-------------------------
Second argument negative - not acceptable. Output as expected.

-------------------------------
$ ./paaiement 10000 -13.5 5 6

        Gebruik: paaiement <bedrag> <rentekoers p.j.> <aantal_jare>
--------------------------------
Arguments > 4 - output as expected.

-------------------------------
$ ./paaiement 10000 -13.5
Fatal error: uncaught exception Invalid_argument("out-of-bound array
or string access")
---------------------------------
Arguments < 4 - unexpected error.

Why did "if Array.length Sys.argv  <> 4 then " not catch this?

The code:
-------------------------------------------
let maandelikse_koers koers = koers /. 100.0/. 12.0;;
let n jare = jare *. 12.0;;
let paaiement rentekoers jare bedrag = 
  (bedrag *. (maandelikse_koers rentekoers) /. (1.0 -. exp 
       ((-.n jare) *. log (1.0 +. (maandelikse_koers rentekoers)))));;

let bedrag = float_of_string Sys.argv.(1);;
let rentekoers = float_of_string Sys.argv.(2);; 
let jare = float_of_string Sys.argv.(3);; 

let main()  = if Array.length Sys.argv  <> 4 then 
        begin
      	  print_string
       "Gebruik: paaiement <bedrag> <rentekoers p.j.> <aantal_jare>\n";
      	  		print_newline();
      			exit 2
    	end 
        else
	 if rentekoers >= 0. then
      	   Printf.printf "\nDie paaiement is R%04.2f\n" 
      		(paaiement rentekoers jare bedrag) 
  	 else
    	    begin
	      Printf.printf 
	      "Die rentekoers (%f) moet tussen 0 en 100.0 wees"  rentekoers  ;  
              print_newline();
       	      exit 2;
      	     end ;;
         
main();
print_newline();
-------------------------------------------------

I am again missing something here.

Regards

Johann
-- 
Johann Spies          Telefoon: 021-808 4036
Informasietegnologie, Universiteit van Stellenbosch

     "He that covereth his sins shall not prosper; but whoso
      confesseth and forsaketh them shall have mercy."      
                                         Proverbs 28:13 
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