[plt-scheme] List Manipulation

Ricardo-

You want to write instead:
>
> (define (wertVonBetrag aValue)
>     (car aValue))

(note that I have removed a pair of parentheses that were wrapped 
around aValue).

In what you had written, you were trying to apply aValue  **as a 
procedure** to zero arguments.  That is why the error message says it 
expected a procedure but was given a list -- specifically, (list 2.0 
euro)


If you are using DrScheme, I recommend that you change your language 
level to Beginning Student.  That way, you will get error messages that 
are more informative for bugs like this.

-Felix

On Jan 7, 2004, at 4:51 AM, Ricardo Massamitsu Nonomura wrote:

>   For list-related administrative tasks:
>   http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>
> Hi All,
>
> I defined a procedure that will take 2 parameters and return a list
> where value is a number and currency is the name of the currency :
>
> (define (neuerGeldbetrag value currency)
>   (list (* value 1.0) currency))
>
> Therefore (neuerGeldbetrag 2 'Euro) => (2.0 euro)
>
> Then I want a new procedure with 1 parameter that will give me the 
> value
> of the currency:
>
> (define (wertVonBetrag aValue)
>     (car (aValue)))
>
> Therefore I was expecting that
>
>  (wertVonBetrag (neuerGeldbetrag 2 'Euro)) => 2.0
>
> I tested the result from neuerGeldbetrag with length, which returns 2,
> so the result is a list. Why car cannot take the head of that list, but
> instead send me the following error msg:
>
> procedure application: expected procedure, given: (2.0 euro) (no
> arguments)
>
>
> Is (2.0 euro) not a list that car can handle???
>
> []
>
>         ________________ _..----====~~~~====--,
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> ===== / /__..---=='---./
> ----- `---'---._________.' Ricardo Massamitsu Nonomura
> E-Mail: massamitsu_nonomura at hotmail.com
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>