[plt-scheme] Combining digits to form numbers

((lambda (l) (string->number (apply string-append (map number->string l))))
 '(1 2 3))
=
123

;P

Robby

On Mon, Feb 16, 2009 at 7:55 PM, Matthias Felleisen
<matthias at ccs.neu.edu> wrote:
>
>> (foldl (lambda (x y) ( + x (* y 10) )) 0 '(1 2 3))
> 123
>
> -- Matthias
>
>
> On Feb 16, 2009, at 8:21 PM, Tim Wawrzynczak wrote:
>
> I think you're looking for something like this?
>
> (foldr (lambda (x y) ( + x (* y 10) )) 0 (reverse '(1 2 3)))
>  = 123
>
>  - inforichland
>
> On Mon, Feb 16, 2009 at 7:08 PM, Thomas Chust <chust at web.de> wrote:
>>
>> 2009-02-16 aditya shukla <adityashukla1983 at gmail.com>:
>> > [...]
>> > (define guess (lambda(lsb csb msb)
>> >         This is the part which i was not able to do , how can i combine
>> > lsb
>> > , csb and msb so the number is of the form (msbcsblsb) .Is there any
>> > function in scheme which can do this
>> >
>> >                          ))
>> > [...]
>>
>> Hello,
>>
>> there are indeed functions in Scheme that can be used do this -- they
>> are called + and * ;-)
>>
>> All you need to do is multiply each digit of the number with the value
>> of its position and add up the results. If you want to create a more
>> general solution for an arbitrary number of digits, a function like
>> foldr comes in handy, too.
>>
>> cu,
>> Thomas
>>
>>
>> --
>> When C++ is your hammer, every problem looks like your thumb.
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