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Re: Sum of squares

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Marcel Hendrix wrote:

> Admit it (when trying it yourself), this exercise is 
> surprisingly tricky. 
> 
> -marcel
> 
> -- -------------------------------------------
> (*
>  * LANGUAGE    : ANS Forth with extensions
>  * PROJECT     : Forth Environments
>  * DESCRIPTION : Sum of squares of two largest of three values
>  * CATEGORY    : Programming exercise 
>  * AUTHOR      : Marcel Hendrix 
>  * LAST CHANGE : March 25, 2012, Marcel Hendrix 
>  *)
> 
> 
> 
> 	NEEDS -miscutil
> 
> 	REVISION -sumsquares "--- Sum of Squares      Version 0.01 ---"
> 
> 	PRIVATES
> 
> DOC
> (*
> 
>   Sum of squares of two largest of three values
> 
>   This exercise comes to us from the book "Structure and Interpretation of 
>   Computer Programs" by Abelson and Sussman (exercise 1.3):
>   
>   Define a procedure that takes three numbers as arguments and returns 
>   the sum of the squares of the two larger numbers.
> *)
> ENDDOC
> 
> : DSQR ( u -- du ) DUP M* ; PRIVATE
> : .ANSWER ( ud -- ) CR ." The sum of the squares of the two larger numbers is " (n,3) ; PRIVATE
> 
> : SOS ( n1 n2 n3 -- )
> 	2DUP > IF  SWAP  ENDIF ( x1) DSQR 2>R
> 	MAX ( x2) DSQR 2R> D+ .ANSWER ;
> 
> 
> : SQR ( u1 -- u2 ) DUP * ; PRIVATE
> : SUM-OF-SQUARES ( n1 n2 n3 -- ) 2DUP > IF  SWAP  ENDIF  SQR -ROT MAX SQR + . ;
> 
> :ABOUT	CR ." Print the sum of the squares of the two larger numbers from {n1, n2, n3}."
> 	CR ." The numbers should have less than 18 digits."
>      	CR ." Try: 1 2 3 SOS            -- print 13, double precision." 
> 	CR ."      1 2 3 SUM-OF-SQUARES -- single precision." ;
> 
> 		.ABOUT -sumsquares CR
> 		DEPRIVE
> 
>                               (* End of Source *)

Factor:

: sos ( a b c -- x )
  3array [ <=> ] sort 2 tail* [ dup * ] map first2 + ;

1 2 3 sos .
13
10 2 3 sos .
109

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Re: Sum of squares "WJ" <w_a_x_man@yahoo.com> - 2013-04-13 17:34 +0000
  Re: Sum of squares Sieur de Bienville <morrimichael@gmail.com> - 2013-04-13 11:43 -0700

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