# [plt-scheme] matrix algebra

 From: Matthias Felleisen (matthias at ccs.neu.edu) Date: Tue Dec 18 19:08:38 EST 2007 Previous message: [plt-scheme] matrix algebra Next message: [plt-scheme] 4.0 question Messages sorted by: [date] [thread] [subject] [author]

```Dybvig's ANSI Scheme book contains a pretty complete solution to your
homework problem -- if my mail client displays things correctly. Your
statement would be better. We could then also point you to the proper
way of learning ...

-- Matthias

On Dec 15, 2007, at 1:05 PM, Justin d. wrote:

>
> i m trying to write a function that implements matrix algebra . I
> saw it on the book exexcise  but i think i need a help coz i m very
> new on scheme
>
> Example
> (1 - 1/3) +[ 2     -1/2] * [ -8     -1/2    3/25 ] +[2       3
> -1]  = [-85/9   -34/15   -408/575   ]
>                 [ 7/3   5   ]   [  7/3    1/5    -9/23]   [1/2
> 1/3   -1] = [-25/6     2/9      -3653/1725]
>
>
>
>>  (mateval  ' (+ (* (- 1 ( 1 3))
>                                                       ( ( 2 ( -1
> 2))     ( (7 3) 5) )
>                                                       ( (-8 (-1 2)
> (3 25) )  ( (7 3) (1 5) (-9 23) ) ) )
>                                                   ( ( 2 3 -1)
> ( ( 1 2)  (1 3) -1 ) )  ) )
> the result
>> ( ( (- 85 9)  (34 15)  (-408 575) )  ( ( -25 6)  (2 9)  (-3653
>> 1725) ) )
>
>  the first expression  , (1 - 1/3) , is not matrix but constant
> and
>           (  1  3 )  is representing  1/3
>            (-  1  2)  is representing -1/2  i mean this is the
> rational representing form
>
>
>
> help me pls
>
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